Got a picture of the bottom mount? I could of swore my directions said 1" from front fender bolt. Maybe I just read it wrong cause it was quick glance.
Follow the directions on the drill. A cheap stamped steel pop riveter is not going to do the job, and the drill is an oddball size that Home Depot doesn't carry. Go to the next size up and the rivet won't seat, next size down and you won't get it in.
You can, if you're careful, ream the hole out with the smaller size.
Lower mount goes in with sheet metal screws, so a smaller size works just fine.
Sorry for the crappy cell pics, but I didn't feel like dragging out the DSLR.