I'm doing it for the same reason. I have my halides lined up parallel with just a flat alum reflector. I want to mount them perpindicular with some type of spiderlight refletor. The pc's I have now are just too big, each of them have the miro 4 reflector from AHsupply. The T5's even with the reflector seem much smaller. But, I planned on using the same workhorse 5 ballast that I'm using with the PC's. Some of the sites I have been looking at sell this ballast with the T5 retrofit.