Kronz...

Your new box sounds super!

Ideally, all the air that's touched by your lights should be 'sealed'... no interaction with the boxes' air. Why don't you build a cool tube? I bought a Bake-A-Round in eBay... waiting for it to start building the cool tube.

Anyways, I think the new dimensions will really help you... I cannot go bigger because, literally, my closet isn't bigger. But, kudos to you!

As to temperatures... well, I think the most important factor for the temperatures is the value of the INcoming temp... I mean, mine is incoming @ 86F... and I've got like a MAX of 91F in my box... usually about 89F or 90F.