Don't know if this would work all day, as an elevated bed would, but for hot summer hikes, my guys wear this
http://www.mightymitedoggear.com/coolvest.html

I wrote a review of various cooling vests (not sure if you can open this if not a member of this forum)
http://mightymitedoggear.com/forum/i...showtopic=5399

another option is zentec stuff. Very expensive, but works.
http://www.mightymitedoggear.com/cratepads.html#zentek

and here's another option for a cool vest
http://www.ruffwear.com/Swamp-Cooler...=2&category=12

(yes, i know I linked to small dog sites, 'cause that's what I have. Everything i linked to comes in bigger sizes)