At a 17w output, this will not be a high energy grow, transpiration rates will be fairly low. The local RH is also between 20-28%, great environment for it. Very dry air will be moving through at all times. Even so, I'll be able to produce several hundred seeds. :)
Plastic should be fine as well. I've always avoided it before, due to the high temps of the lighting, now I don't see where it would really be an issue. With multiple lamps, the heat would definitely be higher, I would look to wood, however thin, instead. Lots of possibilities with these new lamps. :)