Roof rack flooring...

[e9999]

one thing comes to mind and that is that if you're gonna be in the hot sun a lot, an "opaque" flooring will help a good deal with keeping the truck colder

 

[sandcruiser]

open mesh flooring will help about as much, unless you are at noon on the equator-- as soon as the sun hits any angle, the vertical bars will block most of the incident sunlight, but the open weave will allow airflow even if you aren't moving

 

[greenlake cruiser]

fiberglass grating

as i sit here and read this thread, im thinking fiberglass grating for the floor. New thing in industrial construction-in lieu of steel grating--i think you can get it in half inch thickness with like half inch squares. I think it would work sweet

 

[roalco]

one thing comes to mind and that is that if you're gonna be in the hot sun a lot, an "opaque" flooring will help a good deal with keeping the truck colder

X2 on the cooling factor of a solid floor, I run a long low-profile aluminum roof rack (floorboards from a MK V zodiac!) and as well as a great camping and carrying platform, it keep the truck VERY cool in the summer. It's almost like having free AC!