If you do add the fan, I would suggest drilling out the screws so you can take it apart - otherwise I can't think of a way to cut the hole for the fan without risking damaging either the internal components or the wring (if the ballast isn't open you probably have no way of knowing where the wires and compenents are inside the ballast)
FWIW though, the DIY 2x250 ballast box I built with the fan is cool/barely warm to the touch. Another DIY 1x250 ballast box with no fan but good passive venting, that I made is hot to the touch. I have a hamilton 175 ballast with no venting and it is like you described, can't touch it for long without it becoming painful.
FWIW though, the DIY 2x250 ballast box I built with the fan is cool/barely warm to the touch. Another DIY 1x250 ballast box with no fan but good passive venting, that I made is hot to the touch. I have a hamilton 175 ballast with no venting and it is like you described, can't touch it for long without it becoming painful.
