Camp Plus Self-Inflating Sleeping Pad

R Value is cumulative so having 2 stacked pads will increase the total insulation. With that 2.2 + 4.x you'd be in the range you'd want to be for those temps. I use an Exped Dura 8 which is 3.5in thick (8.89cm) and works well for backpacking. When car camping I use a Deep Sleep (R9) that is 3in thick (7.62cm). Since both pads in question are about the same insulation value, I'd lean towards the thicker as long as it doesn't compromise your pack size or weight.

Was sleeping in 26 degree weather this past weekend. I used seatosummit camp plus pad 4.3r and a klymit 0 degree bag. I woke up like at 3am sweaty.

I have a Sea to Summit Camp Plus long and it's extremely comfortable but it's packed size is not small whatsoever. It takes up a lot of room. I have been recommended the Big Agnes Rapide SL insulated several times now. Little over a 4R value so plenty warm for 3 seasons or possibly even 4 if you have a good bag. Another option is the Sea to Summit Ether light XR Pro insulated if you need a warm pad. That one has a rating over 7.4 R value and it packs down dang small for what it is.

I use a seatosummit (camp+) pad for two years now. Pretty happy with it. It provides good thermic isolation (R4.3) for when I use it in hammock but also in tent. Even slept at home sometimes. Mine is semi-foamed, can be inflated pretty tight, small and light. They can last long. I would never go back to those bulky thin foam pads, they do not provide good isolation nor enough padding. Got holes sometimes on trip in Scotland. You can fix it in field. For small pin holes (most frequent) I use a drop of Aquasure+FD, it’s a flexible and waterproof durable glue. For bigger cuts you might need patches. Check this article and video on how to prevent holes, deal with sleeping pad in field and when back home. https://bikepacking.com/plan/best-way-to-patch-a-sleeping-pad/

When I started out on this, I kept seeing suggestions for 3-4" memory foam toppers or such and cutting it to size, so that's what I did. I ended up ditching it, so that was a big waste of money. It wasn't thick enough for one, moisture issues concerned me as well. So I bought Sea to Summit Camp Plus Self-Inflating Foam Sleeping Mat for about $80 which wasn't much more than what I paid for the foam topper and it's been soo much better. It's a hybrid foam/air mattress, so the issues of the foam are limited by being inside the air mattress, and I can get more support in less space by putting air in the thing. The one maintenance thing I have to keep up on with this is that it says you should remove the plug and let the air out if it's going to be in an area where temp changes drastically, like a car. Essentially as the temp gets warmer, the air inside the sleeping mat expands and can rupture it or separate the foam from the liner which would compromise the structure of the mat and likely be uncomfortable to use. So in the morning as part of my routine I just take out the plug so air can just flow out, then fill it up again at night.

https://www.rei.com/product/135417/sea-to-summit-ultralight-air-sleeping-pad?sku=1354170002&store=&CAWELAID=120217890004806433&CAGPSPN=pla&CAAGID=147758271319&CATCI=pla-2077566611927&cm_mmc=PLA_Google%7C21700000001700551_1354170002%7C2077566611927%7Cbrand_flag%7C9920629669&gclsrc=aw.ds&gad_source=1&gad_campaignid=9920629669&gclid=CjwKCAjwg7PDBhBxEiwAf1CVu1fAbcZ3QQVWH-mwf-AhewUlIW05eSDZS31n8v4YuCkqF1QmiNAjpBoC9q0QAvD_BwE Or this slightly heavier one for $100-$109 https://www.rei.com/product/199005/sea-to-summit-camp-plus-self-inflating-sleeping-pad-mummy

I had a Klymit Static V Luxe (the extra wide one) and while it's decent enough, I upgraded to a Sea-To-Summit Camp Plus self inflating mat, and that one is way more comfy for me (I'm a side sleeper). It has a much better R value to boot, I think 4.3 vs 1.3 for the non-insulated static V. It does take up more room in the top box but it's worth it to me for the better sleep. I think it's about the same price as well.