Emmery:

Since it is go/no-go type gauging, I don't think the placement of the coin is critical. I hold the hammer and flange horizontally, place the coin so the center is about where the hole for the screw is and let go. I have used the traditional test of using the screw, also, but finding the point where it slowly droops is pretty tricky. And I really think that the best friction, especially when freshly re-bushed, is when the flange can just barely hold the screw. YMMV

Thought I'd share -
The Mannino broaches are rather difficult to put back in their pouch. I asked Don about making some sort of sleeve for them to make them easier to insert. This is what he said:

"The reason the broaches are hard to insert is because they are made too sharp. The easiest thing to do is round the tip just a little, then polish the tapered tip area. This keeps the broach from snagging the cloth in the holder, and also makes the reaming process work better."

He mentioned that some people use coffee stirrers in the pouch, but if you dull the point, they are not necessary.

I'll try it today and let you know how it goes.

Task completed.
Absolutely a huge improvement in ease of inserting into both the pouch and the flanges!
Highly recommended modification.
Don said that he instructed Schaff to fix this in the future so if you get a new set, you might not need it.
I would also recommend clear coating the size markings so they don't rub off. I plan on getting a white paint marker and putting one circle around the handle for 51, two for 52 etc. etc. Then following with a clear coat. This will make identification quicker and easier.
Cheers!