[Bruce Lancaster]

But note also the difference between gears is reduced a bit by deeper flange there. You need to do something like setting the flanges on a known size block and measuring thus to friction surface and to ring gear location so you can get truly comparable results. The practical questions are whether the gear winds up in the working travel of the starter drive and whether the thing clears the block and then whether main surface is not too far off...
I actually measured a bunch of this when I got hold of Ron's book years ago, but lost interest because I had a decent supply of properly matched flywheels. I blocked up the wheels on their crank flanges with sockets that were 1" long to make the arithmetic simple...