I've tried everything from the paper clip "spring," to the rubber band, to a trimmed-down plastic card/shim and the fit still leaves something to be desired... sometimes mine doesn't chime at all or, if it does (after a whack to the right side), it's not stable until I pop the case, take out the board and give the ROM a tune-up, fit-wise. I don't blame Doug for the design at all - it's got to be a tough supply chain and next to impossible to capture like .76 mm (the difference between .50" and .47" as you noted above) like 25+ years later.