I got up early this morning, and decided to save a bit of time at the shop by doing the measurements to figure out where the holes go. I measured everything up carefully, and marked the spots to drill with pencil marks on masking tape. I double and triple checked my measurements to make sure I got everything right.
After I got to the shop, I thought about it for a bit, and realized I'd really already done the hard part, all that was left was to drill the holes. I've got a drill, why should I pay someone else $50 just to make a hole?
So I went and bought some titanium drill bits, some mounting tape, a couple nuts, some touchup paint and a small tube of silicone sealant. Total cost, about $20, and I have stuff left over.
I got home, plugged in my drill, and started with a pilot hole. The titanium drill bits were a good buy, they bored through the steel like a pencil through butter. I stepped up to a larger size bit to expand the hole, then the final 1/4" bit, just slightly larger than the size of the bolts on the spoiler.
I tested the fit of the spoiler to see if I needed to tweak the holes any... And it was an absolute perfect fit, on the first try! Whoo!
I put a bit of the touchup paint on the insides of the holes (to hopefully prevent rust), and while I waited for that to dry, I set about cleaning the paint and the spoiler and applying the mounting tape.
Unfortunately it started raining before the paint finished drying, so I moved everything into the garage. I'll probably finish it Sunday. I just need to remove the cover from the mounting tape, drop the spoiler into place, apply a bit of silicone caulk on the inside of the trunk to keep the water out, then install the nuts.