After suffering through several shonky mounts I finally discoverd the K-tek KSM shockmount. It is incredibly solid and locks positively and quickly at any angle. No more mic fluff in shot. http://www.mklemme.com/pole/ksm.html
I mounted a 3/8 thread directly onto the camera (a Sony) in place of the 'clamp' mount and it works well. Ideally the mount would have a quick release solution, as it is it takes half a dozen turns to attach/detach the mount.
There may be a way to securely fix a 3/8 thread to the HVX. Otherwise K-tek have a 3/8 adaptor that fits in the standard 'clamp' mic mounts, and this may also be a good solution. http://www.mklemme.com/pole/kbwc.html
Hotshoe to 3/8 thread adaptors are available but I suspect that a mic would place too much strain on the hotshoe.
The K-tek KSM costs a lot more than some of the other offerings but it sure beats screwing around with wayward microphones.
Thank you for the tip Russell. The K-TEK mount is way to go. A reliable soundequipment-store in Amsterdam -Noiz Boyz- told me also. I don't no how much rumble it will give with my 418, MS-stereo Sennheiser, 's very sensitive mic. I have to test it.