Yea I do image that going to HID would add a bit of heat, those things are HOT. but you could always add another small fan blowing between the plants and the light , directly towords and exhaust port, and you'd be totaly fine.

They look good man, nice fat buds always do...

I think Im going to give mine a bit of a hair cut this weekend too ( im the same as you , about 40 days flowering )

Peace

JJ