PCBgogo

Those of you successfully doing do it PCB with the photo method: what clear material do you suggest for cleaning the transparency sheet to the PCB? I have been using a piece of glass from a picture frame, with a heavy object to hold it tight, but there has still been issues with uneven clamping of the glass to the board letting light in from the sides.
I'd like to make a purpose built framem of sorts.
Does acrylic work well?  I like the idea of a material I can easily drill holes through. Sadly, the only stuff I have found locally is treated to not pass UV (to protect photos). Obviously that's no good.
Where would you get acrylic (or some other cut-able, UV passing material)?
Can glass be drilled easily? 
Also, I have been using an aquarium light fixture with four T5 HO 10,000k 24  watt bulbs. They are 21 1/2"  long. I realize those aren't specifically UV, but they have been kinda working. I get fast exposures, and I'm still thinking the inconsistency is due to my glass not pushing hard enough, consistently across the PCB. That said, is there a bulb out there that is better, that would fit this fixture?
Finally, if I build a box, should the inner material be light reflective, or absorbent? My gut says absorbent, so the only light comes from the bulbs above. That way no light gets in from the side, which I think is part of my trouble.
My results are tantalizingly close to the kinda specs I need! Every attempt is just a section or two on a mid sized PCB from bring usable, so I know I can do it. 20/20 track/clearance for sure, and sections of 10/10 that came out well. 
My current project is a 6502 single board computer. It's working well on a bread board at 1 megahertz. I feel a diy double sided PCB is reasonable to attempt for this.