The issue with shims is that poorly applied they can substantially reduce the crown's ability to clamp the steerer. You have twice the amount of pinching down to tighten the crown clamp. One is that of the steerer inside the shim, the other is the shim's OD in the crown. As there's no suspenders (as in belt and...) with a fork I would be very careful on how I made sure the crown/steerer were secured as well as how the crown's future fatigue/stress life is dealt with. (Belt and suspenders" as in every frame tube, but the steerer/crown, is joined at both ends. So a joint failure on a stay or main tube still has the other end to carry the loads for at least a little while. But the crown/blades are only connected to the rest of the bike via one joint at the steerer's base) Andy