Nice work Mike! Only just now seeing this latest stuff, busy with Moab stuff for some reason.
Anyhoo, here are some things to consider: You ALWAYs want the rear main a little looser (more clearance) than 1, 2 and 3 because it has a larger surface area. Like wise, you torque the bolts down less because they're smaller and there's 4 of them. Your 0.0020" should be just fine.
In the real world, your rod bearings are more critical (bolt torque and oil clearance) - they're always the ones to let loose when anything lets loose.
Finally, 2Fs DO NOT use shims, F motors do. When you add a shim, you increase the clearance. We had to add shims when we were assembling the F for my 71 because it was way too tight without any shims and you couldn't even turn the crank.