
Exped
MegaMat Series
Car camping comfort champ, but some side sleepers find it thin.

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No the sleeping bag won’t help much. To get a significant bump in comfort you’ll have to jump into some heavier pads that are still compressible enough to bring backpacking. Pads like the Thermarest Neoloft or Exped Megamat Ultra. I have a Tensor All Season and find it comfortable, however my Exped Synmat 3D (older version of the Megamat Ultra) is definitely more comfortable. My brother has the Rapide SL which is similar to the Tensor in comfort.
Second for the Megamat Ultra. It’s a big jump in comfort over any ultralight pad. Depending upon how far I’m hiking I’ll bring it over my Tensor All Season which is a decently comfortable pad in its own right.
I have the predecessor to the Megamat Ultra and it’s amazing, so I’d check out the Ultra. The other mat to consider is the Neoloft, which should be close in comfort but packs smaller. There will be a noticeable jump in comfort between either of these and ultralight pads like the Tensor All Season which I use for backpacking. My Exped is what I take on rafting/kayaking trips where weight doesn’t matter but volume still does. The foam pads like the regular Megamat are more comfortable but they pack down huge and will take up too much room in the raft, avoid foam if pack size matters. Those are car camping pads.
You mean backpacking? The Megamat ultra is my favorite comfort oriented pad that you can use backpacking but it’s pretty bulky, but for shorter distances or more base camp oriented backpacking trips it’s fine. The Thermarest Neoloft packs smaller while still being very comfortable so that’s a nice compromise. If you are pushing miles, the Rapide SL, Nemo Eclipse, Exped Ultra 6.5 are really good.
I’m 220lbs and never had issues bottoming out even with my old 3in summer backpacking air mat. Are you adding enough air? I also store my foam/air mattress compressed. Are you looking for full foam or the more common air/foam (Megamat style). You also mentioned fiberglass so I have no idea what you’re talking about. I’ve never heard of a camp mat containing fiberglass. My air/foam car camping mat is a generic one I found on Amazon. I love its integrated pump which I’ve used to inflate other pads as well as stoke fires. It was dirt cheap, not quite as comfortable as a real Megamat, but close enough considering it was well under $100. It’s similar to the Heeta and Pinehike 4in pads that are on Amazon, the tan detachable pump is exactly the same.
Exped Megamat Ultra. It’s all air, no foam, and has synthetic insulation. It does have vertical baffles like the BA Divide, but the top fabric is stretchy and I don’t notice them. The downside is that it’s about 2lbs. I’ll add that my previous pad was an Exped Ultra, and the verticals baffles on that were not particularly comfortable. The Megamat Ultra feels completely different. It also doesn’t have the “side rail” cradle shape that the regular Ultra has, so it is a flat surface.
What previous brands did you have? The Exped MegaMat is a pretty popular one and on sale at their site and REI right now. I just ordered one because my backpacking pad is just too uncomfortable for longer car camping trips. I tried out the Hest foamy at REI and while it’s comfy, it also stores huge and more than I wanted to spend.
I’ve seen reviews that MegaMats have lasted that long! Exped has a 5 year warranty, and I’ve seen people say they’ve gotten items replaced even after the warranty was up. REI’s is only 1 year on their branded gear. I tried the REI’s comparable pad, the westward dreamer, and it was comfy, but the Exped warranty and higher R value was worth the extra $50 to me.
The Ultralight is certainly lighter, and a comfy pad compared to a lot on the market, but the Flex Air is on par with Thermarest Neoloft and Exped Megamat Ultra, except lighter and less balloon-like compared to the Neoloft.
In the states REI and other outfitter stores let you test them out. Is there an option at a store by you to do that? I am a very picky side sleeper and the exped megamat (4”) has been fantastic for me. I toss a bit so the 30” wide version is perfect.
The Megamat *Ultra* is *chef’s kiss* comfy for backpacking, although definitely on the heavier side.
Get something with a super high R rating - higher than you think you need. Look for a baffling system that is either dimpled or vertical. For whatever reason, horizontal baffles don’t have a lot of “give” to them so they are less comfortable for side sleepers in general. Therm-a-Rest Neoair Xtherm is probably the warmest pad out there (not the highest R rating per se but the most effective insulation system means it is still warmer than other pads with higher R values). It may not the most comfortable for a side sleeper because of the horizontal baffles, however. But this is the pad you want if you want to prioritize warmth. If you want to prioritize comfort, Sea to Summit Ether Light XR Pro will probably not sleep as warm but will be more comfortable for a side sleeper because of the dimpled baffling system. Nemo Tensor Extreme Conditions is also very warm and only slightly less comfy than the Ether Light. Exped Ultra 7R is a bit heavier and bulkier but is very comfy for a side sleeper. It uses down rather than reflective film for insulation. So it won’t be quite as crinkly as a lot of warm pads, but I’m not sure if the down insulation is more or less effective in this application. Big Agnes Campmeister Deluxe is quite bulky and heavy for a backpacking pad but is super, super comfortable and has a very respectable R value of 7. The other big, bulky “luxury” comfort backpacking pads - Exped Megamat Ultra and Therm-a-Rest Neoloft - are great options for comfort but with lower R values so they may be less warm than you might want. Other things to consider - even a well-insulated sleeping pad will only stay as warm as your body is able to heat it. The bigger the pad, the more of your body’s heat it will draw away from you. So don’t buy a massively oversized sleeping pad thinking it will automatically be more comfortable. For insulating purposes, something that is only as big as you need it to be will be more efficient for your body to keep warm. Make sure you take advantage of all the usual strategies for staying warm in the backcountry: Use your Nalgene as a hot water bottle and keep it in your sleeping bag/quilt with at night. Do some jumping jacks or other activity to get your heartrate and body temperature up before going to bed. Make sure you are properly hydrated and getting enough food to keep warm. Etc.
Megamat Ultra and the Thermarest Neoloft are comparables. Def not ultralight but I use the Thermarest on backpacking trips, not thru-hikes, and love it. I'm a big guy and the Thermarest is comparable to my MondoKing and Exped MegaMat Duo. The Ultra will work well for you.
Guy on ytube who reviews western mountaineering sleeping bags sleeps or slept on his exped megamat for yrs. He discusses it there. I occasionally break out one of my mats and sleep on it; I miss camping that much.

Exped
MegaMat Series
Car camping comfort champ, but some side sleepers find it thin.

Exped
Ultra Series
Lightweight side-sleeper comfort, but a bit pricey and bulky.

NEMO
Tensor Series
Ultralight side-sleeper comfort, but slippery and prone to leaks.

Big Agnes
Rapide SL Insulated Sleeping Pad
Comfortable with side rails, but heavy and warmth claims disputed.

Therm-a-Rest
NeoLoft™ Sleeping Pad
Very comfortable, good service, but heavy and bulky for backpacking.

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Therm-a-Rest - NeoAir Xtherm Series