frameless packs with inflatable pads

the tension of the packed stuff inside seems to be structure enough

with my blast 18 i just fold up my BA aircore & put that against my back, then fill the pack with my other stuff

seems to carry well that way

i think it would only be a potential problem with a much larger pack & more weight

but for under 20lb loads, I've been fine doing as above

This doesn't directly answer your question but I'll chime in with my experience, since I had the same question. I've been using frameless ULA packs with inflated Thermarest for 7 years. I just switched to the NeoAir on my most recent 11-day trip. I solved the frame-structure problem by using 4 sections of z-rest for structure and just packing the NeoAir with my sleeping bag. It worked out just fine up to ~30 pounds, above that was workable but not so comfortable.

My second solution to the problem was to order a ULA Ohm pack which arrived yesterday. I've only worn it around the house, but it sure seems like the diminutive frame in that pack eliminates the need for any additional structure; and by packing the sleeping bag and clothing against my back it won't need any pad. As usual, Brian has produced a very well designed and well executed product – he rocks.

Amy

If you're using a thermarest as a cylinder, don't forget to blow some air into the pad once you have it inside your backpack. It's flimsy and not supportive otherwise.

I would say Amy has highlited one of the problems with the NeoAir, if you use a foam pad for pack structure.
A foam pad is obviously lighter than the NeoAir, so your pack weight will increas if you swap.
If like Amy you still use a Ridgerest as a frame, then you are still carrying the weight of the Ridgerest plus the NeoAir.
That's ok if like most folk on here you are trying to increase the weight of your pack. ;)

These are my main strategies thus far:

1. Torso length air mat + Ridgerest cut to bacpack panel size for under feet when sleeping.

2. Torso length air mat + full length 1/8" GG Thinlight pad forming cylinder inside pack. (better cooler weather option)

3. Option 1 or 2 + lightweight chair kit folded strategically and placed behind foam pad for extra rigidity. (better for heavy loads and longer trips? – yet to try)