In my experience with the "Evo" brakes (ie 320mm diameter discs as opposed to (iirc) 300mm on the earlier bikes) as fitted to my Rocksters : it's the Tokico callipers that tend to be somewhat problematic in that regard. The Brembos, as fitted to the GSA, are much better. My thoughts are that the Tokicos have a much greater difference in the diameter of the pistons and the piston-bores so they allow a lot more crud to be in, and thus work its way behind the seals. I've done the swap 3 times now and Motorworks know me well enough that they always correct me when I order discs...

(Ideally you need to use the same discs as the GSA as well. I've run the bike with the standard discs and they work fine, but the swept area is slightly different).
(I'm sure you know all this Dr. Farkoff - I was more writing it out for other readers.

)