My HID kit will be here today, so I will be putting it in today after I get it. The thing is, it doesn't come with the mounting brackets like some of the other kits do. It has threaded holes to bolt it onto a spot with, but I'm not sure if I'll be mount them cleanly and kinda hidden if I do that. Thats why I want to know how hot they get, I might just use a bunch of heavy duty velcro to hold it on or maybe even get down right ghetto and use a couple zipties if I can find a good hidden spot. But I obviously don't want to do that if the ballast gets any hotter then just slightly warm to the touch.
Heres a big picture of the ballast (not my pic, or the companies pic but the ballast is the same)