Thank you all for your input. Sorry I have been absent from this discussion, as I have had much difficulty signing in to the USFG site.
I am concerned that anything I add to this discussion will make an already confusing minimum size rule more confusing. My understanding is that there is no actual maximum gem size specified. So the way to stay well away from this issue is to keep your final gem size well above 10 mm. Anything over a final 9.9 mm is acceptable, as explained by Gordon above.