Curious if all 6 bolts even go through. On an FZ1 tank it was 3 or 4, the others were decorative and only threaded into the gas cap.You might be better off drilling & tapping a new hole off to the side (at least 1 hole diameter is probably best) in the tank ring, then matching one in the pump flange. IOW, moving the bolt over. or even 2 new ones, one on each side of the old one.
Easier said than done of course. I'd want to do the drilling in a drill press, since it's a blind hole and you really don't want to drill too deep. Most drill presses don't have a table big enough for the tank. Might be a chore to somehow hold the tank square for drilling. Tapping the new holes would be the easy part, comparatively.
Possibly you have enough clamping force with only 5 out of 6 bolts, but if it were my bike that would bug me. Sure would be awkward if it started leaking.