Yes they need to be glued in place. You cant buy the shims. From what I understand using a dremel and starting with something like brass you make two C shaped shims about .190 inch thick and glue them in using RTV. There is plenty of drop-out left so that the whell is still held secure. One guy is using the 451-28 Stelvio says the ride comfort factor went up with the -28.
Randy S has taken this up with the factory and they seem non-plussed about it. Dont know if you can grind carbon fiber but that may be another way to go.
