First off the heat to light ratio is worse for cfls, and you wont get the same amount of lumens per watt. Plus they cant be air cooled. The reflector you are showing is air-coolable so you should either run a 6" duct fan through it (cheap and loud) or a centrifugal fan (more expensive and quiet). Do that and you'll be able to stick you balls against the reflector glass with no prob (wouldn't recommend this). That digi ballast will emit minimal minimal heat with a 250. As far as sticking the reflector on the top of the cab, just watch out for light leaks, and dont start a fire!! If I were to put the reflector on the top the of cab I would be sure to air cool it. Good luck and peace