Exactly - if there is any clearance at all -- tight or lose compared to spec -- it can be measured, and the correct shim ascertained in one shot.
If the clearance is zero, there is no way to determine the correct shim in one shot. You have to gain clearance with a small shim, then get the clearance in spec with a second shim.
Before you go buying shims... read the manual on the section about crank shaft position for checking the shim values: it is easy to try to measure the clearance in the wrong position and find zero clearance.
When they say Harleys are for 1%ers, I don't think they mean guys who sell crank and get in bar fights any more.