Modifying the original rear shock (Sachs)

[CTD]

Hi,
I have found a great set up for me on my S1000RR: for road use only, and my weight at 70kg (154 lbs).
Adjusted rear ride height (eccentic washer), and front & rear preload to get ideal sag, etc. Dampings of front & rear, compression & rebound works great on standard settings.
The ONLY issue is that the rear High Speed Compression damping even at the lowest setting of 1 is still too hard.
Is it possible for a service center to adjust the Sachs rear shock internals so as to ONLY reduce the High Speed compression. And who can do this preferably either in Belgium, Netherland or Germany? Thanks. CTD