Just put together this bike which is a VB-r-068, i've tightened it to the point where I can't tighten it anymore yet I can still tilt it and what not. I've greased the threads since I thought that might be the issue. This is steel rails I believe, it is the EC90 "power saddle".
Seat post showing the hole for the clamp (click for larger):
Clamp mechanism parts (click for larger):
View of the clamp holding the seat rail of the mounted saddle (click for larger):
View of the mounted saddle from behind, showing the clamp (click for larger):
Assembled clamp mechanism (click for larger):