Drilling stainless steel

I've been working on the stuff under the seat to hold the battery, fuse box, starter relay, CDI unit etc and making some plates from alloy plate. Which was fine and no problem. However life got a bit more difficult when it came to drilling some holes in the stainless steel plate - my HSS drills seemed to have little impact, so after some internet research I've getting hold of some cobolt drills. I also found out that heat, through drilling, can make SS harder so you have to take it slow and easy....hmmmm...