I'm a big fan and long term Exped user. However, recently I've been waking up with a definite ache in the small of my back. After some thinking, I'm wondering whether baffles laid short ways such as those used by Neoair might actually deform more readily and therefor offer a greater degree of support than the length ways baffles used by Exped?

Anyone? ... and it's not pressure related although that would obviously be the first thought.

Its an age thing once you pass 50

I sleep on my side so mebbes different for me - I've always been put off expeds because of the longitudinal baffles as they are quite pronounced so I reckoned they would make lying on my side a bit awkward, or at least with less comfort than on the neoair. The ripples on the neoair are fairly shallow and being across your body don't affect your lying position. I guess if you are lying on your back then an neoair would conform to your body better as it flexible whereas the expeds won't be. I suspect an exped would be better for river rafting though

I do consider myself a side sleeper but I'm pretty sure I change position throughout the night. Your thinking would seem to back my thoughts up Phil.

'Spose you'd need to try them back to back....
As it happens my neoair is currently stuck in customs 3 weeks after sending it back to Cascade in Ireland for a warranty replacement after some of it's baffles blew - kind of gave it a built in pillow. So I might end up on the ground for my April bivvy at this rate.....

I have an Exped mat (Synmat 7) and a Thermarest Neo Air X Lite and I get the same lower back pain and stiffness on both of them. I did go through a phase of believing that it was related to having them too firmly inflated but it now seems to happen irrespective of pressures.
I'm now 58 and I've put it down to old age since I don't recall it being an issue until fairly recently. Sorry if this isn't the answer you were hoping for.