Just out of curiosity is the frame geometry of the PDS bikes different to that of the earlier models with the WP or Ohlins linked shock or are the spring rates and damping completely different. The 97 FC 501 that I have (WP 50mm forks and Ohlins shock) doesn’t get head shake even with the forks slid up 10mm in the clamps. The suspension hasn’t been revalved just dialled in with the clickers and sag set.