Homebrew PCBs

Hello,

I just got two 8W blacklight tubes, and have build some kind of
exposure stand. I put the tubes on the bottom, facing up, and 7 cm
above there is a transparent 0.5mm crystal. On top of it, it will be
the PCB, facing down, with some weigth on it. Do you think this will work?

I just find some problem with this approach:
- No reflector, is it really necesary?
- Maybe 7cm is too close to the blacklight tubes... I really don't
know if it will be done in 2 minutes, or 6. But anyway, is it too close?

Thank you