I more or less just centered it in that opening between all the hood bracing. Didn't cut into any of them. My "rivet" hole is covered by a brace. I just drilled thru both brace and hood surface anyway and it works fine, but the provided rivet would be too short. I didn't plan to use the rivet anyway. Instead I helicoiled the plastic rivet hole in the tach and used a machine screw in place of a rivet. I just used a hole saw itself to locate the center of the circle instead of roll of tape.

Illumination is bright. I'd almost say too bright. Draws attention to itself. It's certainly easy to read night and day.