I just Bought one of these, but decided to call the manufacturer before drilling a hole in the top. I talked to some B*#!# who immediately said no you cant drill a hole in the top. I asked her if she has seen the schematics for it. She only said it had been asked before and the answer is no! She snickered too, like I was an idiot for asking.
Anyways, It would be nice to know from anyone with real world experience if they hit a coil while drilling on top.