Carol says: "The Cyclone also makes an acceptable chair when combined with twenty-inch wide foam pads and even the less-than-twenty-inch wide Bozeman Mountain Works TorsoLite pad. Without the stiffness of an inflatable pad, the resultant chair is not as comfortable, since the chair collapses around the user's torso and legs, but it still provides good back support."
I think that's a wee bit of an understatement... In my case (I'm 5'10/150 lbs), when using the BMW TorsoLite the aluminum stays really dig in to both my ribs and legs. If you want comfort (that's why you're carrying this, right?) I think you should plan on using a full 20" wide pad.
I tried my TAR Prolite 3 Full Length, and it was markedly more comfortable than the TorsoLite (which I otherwise LOVE, just not for this purpose, sigh...).
I also have a Pacific Outdoor Equipment - Max Thermo 72" x 20" x 2.5" Inflatable Pad, and it is somewhat less comfortable than the TAR PL 3 as it is cut in a mummy style (Narrower at the head and foot) which allows the aluminum stays in the chair to dig in rather uncomfortably, though much less so than with the BMW TL. One possible workaround for the mummy shape pad, however,is that if you fold the mattress so that its center is situated in the center of the chair, folding the two ends inward to also meet at the chair's center, it will not collapse as readily. Surprisingly, it stays in the chair pretty well in this configuration. I expected it to squirt out...
Regarding the use of a 20" wide foam pad, I'm also a bit skeptical. I think it would have to be a pretty firm foam in order to keep the chair from collapsing inward.