Seriously, the best lensboard method I've settled on myself is to forget about metal lensboards and fabricate them out of hobby plywood from the hobby shop. With ingenuity, you can make an exact replica or BETTER doing it this way. That way an ordinary brace and bit with adjustable bit is used to bore the hole slightly smaller, then sanded to fit the lens perfectly. I am very happy with all the lensboards I fabricated this way. And the cost was perhaps 2 dollars for materials. I would never consider going back to factory-made lens boards. Mine are beautiful and trustworthy.