Bangin' out some mounting tabs on the sissy bar today. Heat, Hit, Heat, Hit, Heat, Hit, Heat, Hit, Heat, Hit, Heat, Hit, Heat, Hit, Heat, Hit, Heat, Hit, Heat, Hit. Found an old school article on building sissies and this was the "technique"they described. Worked better than I expected to be honest.

Inside surface with hammer marks and edges rounded with bench grinder.

Outside surface flattened from concrete floor I was bashin' against.

Measure twice drill once.