There are some things worth attending to. I have a 5x8.. and the first thing I noticed was how much it would hop when crossing railways, no matter how slow you drive. I then removed the middle spring and the trailer is so much nicer now.
As far as heat effects? I couldnt have it worse as my trailer is black. I bought a couple of vents and installed them at the top on the walls, kitty corner so as to let it breath. Equaly important.. I insulated the roof with 1" aluminum foil backed insulation board. This I felt was very important because the roof is nothing more than a shinny 1/8 peice of aluminum shaped like a radar dish and focusing the radiant heat inward.