I have the cheapo 1/4" clear glass (no UV coating) on my DIY unit and it works fine.
Slight tangent, but I am using an Olec 5k with SP1400 (with diazo) and from 28" away it takes me 100 ltu's/seconds for a hard 7 on 225S mesh (1/1 coat, low OEM though I can't give you an exact percentage). I would push the light closer (according to the math discussed in a previous thread I should be able to have it as close as 18") but that wouldn't allow my glass/frame to flip up for exposure. Seems like this may be abnormally long. Wondering if there is anything I should do to speed things up. 100 seconds honestly works out pretty well for my exposure cycle, but speeding it up about 30 seconds a screen would let me get behind a bit vs having any down time.