Definitely no issue with heat, the unit is only 1,100 watts. The screens now sit 4.5" lower than on the glass and thanks to the inverse square law the benefit in exposure time not to mention removing the glass form the equation is working out quite well for my unit. It may not have the same returns on a much more powerful light point obviously, but for us lower power units this can give some good returns for the little bit of work needed.
Before modifying we just laid the screen on two standoffs on the glass, we never could get the burn time to be less than the printing time so it always bottle necked at the exposure unit. Now it burns much faster than the unit prints which is great for us.