I called Timney again and got transferred to a guy who said the sear hole being too small would not stop the bolt from opening.
He said I could keep the shim or grind a few thousands off the top of the Timney sear.
He says he personally would grind rather than shim, to keep the parts count down.

I tried two 1903 Turk receivers and bolts had the same need for a shim with the Timney.

There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. -Ernest Hemingway
The man who makes no mistakes does not usually make anything.-- Edward John Phelps