Shimming a reamer is not unheard of. Brass and soft steel work best, and don't really show mark from reamer. The flutes of a reamer don't so much cut along the length, only the first small portion. Their action is more burnishing of tool marks. They taper away [less] from the tip.
Normally the shim is cut resembling a iso-triangle. The point, inserted between a pair of flutes holds it in place, the shape allows a gradual increase of diameter without collapsing shim or jamming in hole. Get results by steady feed rate, as the uncovered corner edges produce something like boring.