A friend converted an overhead projector (and a 1080p LCD panel) into a DIY projector, some years ago. His panel turned brown and broke because of too high air temperature.
As even the OP has cooling issues - lesson learned: Better use LED with 1000+ Lumen instead of a halogen/xenon lamp.
It seems OP uses the arc lamp for its almost-point-source qualities. Halfway down the first page he simulates a led source, it will create a less sharp focal point.
A friend converted an overhead projector (and a 1080p LCD panel) into a DIY projector, some years ago. His panel turned brown and broke because of too high air temperature.
As even the OP has cooling issues - lesson learned: Better use LED with 1000+ Lumen instead of a halogen/xenon lamp.