I ended up using a 3/8 drill bit.works good.
Vaughn is right about the circle cutter,can be very finiky.I have what is called a roto-broach,can cut hole in sheetmetal in 10 seconds at 100rpms and you have to be REAL careful not to cut through both pieces.
I also have the spot weld cutter bit from snap-on,works OK in a hand drill but like vaughn said it takes a bit longer.
