The CAIR folks say, "Air is captured at atmospheric pressure in an open-celled foam and sealed in the Air Cushion. Once the air cushion is welded the open-celled foam becomes irrelevant, as it is the air trapped in the cushion, which is doing the work.
At 5,000' MSL, the atmosphere is 83% of sea level, so the panels should be about 20% larger with no one sitting on them. I don't know how that would affect things after you sit on them, but it SEEMS like with would be somewhat overinflated. I noticed the CAIR manufacturer says there isn't a significant change with temperature ("There is minimal affect of temperature on the CAIRŪ Air Panels. For a 30 degree (Celsius) change in temperature there is approximately 1% change in expansion of the Air Panel."), but leaves altitude unmentioned. Is that because a 20% expansion IS significant?