Hi Joris,
Yes, this is true.... some of the manual focus PQS lenses will not reach 1/1000 with the Hy6, but the solution is to clip a resistor or diode on the circuit board of the lens. Depending on the lens it can be easy or hard to reach. I'll dig up the information and post this to my blog next week sometime. Naturally, DHW can of course do this service for you.
Regards,
Eric