I have a little movement with the 1 1/2" hole saw but bushings seem to hold in place and fit into hole with no force. The rear hole that I replaced with 1/8" plate single layer personally seemed easier than double layer with thinner material and bushings are a great fit. more than likely no 2 holesaws will be the same thickness so allow for that before drilling, I used milwaukee brand they have a fairly thick wall
Jerry Tallman 69 455/4sp Windward Blue, deluxe parchment bench seat, under major restoration je_tallman@yahoo.com