hi rossi,
is the gtx-r clearing the headtube okay? i'd an issue with a snafu mobeus on a pantera where the inner diameter (ID) of the mobeus (gyro) was too small to clear the headtube and had to do without it. (put on a gtx (the heavier one) instead.
any other gyros u can try? (the gtx-r has a smaller ID than the gtx)
also check the top bearing cover on ur hidden headset. this may be sitting proud of ur headtube, ie bigger diameter, and the gyro's maybe hitting it.
Bp.