Yea man, the idea is cool and all, but I have to post my thoughts on it.
I was happy as shit to find a cheaper method of air cooling my lights, as I have 3 going. But after buying the bake-a-rounds and screwing around with different dimensions of pipe between them all, and using a 6" Vortex reduced to 4", I have come to the realization that the bake-a-rounds are not big enough inside to use 600w bulbs. Granted, I do use 3 bulbs, so I am not getting the cooling that a guy would get off 1 or 2 bulbs. But the bulb and socket and bracket take up so much internal space, that you are only getting a minimal amount of flowing air around all that. I mean they do run cooler than non air cooled lights, but not enough of a again to spend the money on it, and 3/4 of the internal volume is taken up with socket and bracket.
I managed to find proper 6" air cannons for $80 each so I jumped on that. They haven't come in yet, but I am positive that with the increased volume, the lights will work like an air cooled light should. With the price of the bake a rounds and shipping and epoxy and ducting and reducers, I paid almost as much as just buying store boughts.
Not to rain on the parade or put down this idea, as I'm sure it works mint with one or 2 lights, but just if you were thinking of cooling more lights than that in a row, then take my advice and look into a bigger glass.