I am honestly not positive it does have a cap as i have not (knock on wood) had to tear one down yet, but looking in there is something that looks out of place on a fan and i suspect it to be a cap, but like i said have not actually torn into one.
I am sure i could get better cooling out of them with straighter runs, but with a 7x7 room, no floor space for the filter, and only one air cooled hood at the moment, it is not as perfect as it could be, but only 2 90 degree turns, otherwise dead straight. At this point i am just exhausting and intaking from the same area the grow is in, but if things get to hot, i will add the 400 sq ft basement into it, dropping intake temp. Thanks for the tips, i wish i could have the many lights, one day i may switch to 4 600s instead of the 2 1000's, but i have specific hoods that i want, and the are expensive.