I used to keep my temp between 81-82. I get a good 3 degree bump. I think bigger fans would help. A well ventelated canopy should be fine but I can't speak from experience yet. I hate have in the fan on the sump but it does not hurt. Would not work for you though.
*180 gal Display, 100 gal basement sump, 33 gal refugium, 3x250 MH, 2x160 VHO actinics, zoos, some softies, LPS & lots of acros and other SPS.
*100 gal prop tank plumbed into main system w/ 2x96 PC lights and 1x150 MH,