Not meaning to jump in here. I know Len and Pinwheel forgot more yesterday than I know. Pinwheels of course right like always.Better to fix the problem, rather than bandaid it. PA,s on the right track and brings up an interesting thought. How about a pendallum sight that swings off center, side to side, and forget the bubble entirely. Should be fairly accurate out to 30 yds. or so. Not up to Pins standards of accuracy, but theoretically it should work to a degree. Vertical impact points would change slightly. How much I have no idea. Oh well, still not the stupidist idea Ive had. Someday Ill tell ya about the motor I designed that runs on steam. I still think that idea has merit. Im probably just to far ahead of the times.