I just bought the docking collars for the Gorelock 2 and just as I figured, they don't properly fit our rig. They DO fit, but down on the post and flush bellow the top post clamp. If you noticed how the Tiffen docking collar fits over the bottom of the top post clamp, this allows for about another 1/3" clearance for the gimbal. It might not seem like much, but if your switching to the Gorelock, you will already lose close to 3/4" between the collar and the gimbal in order to dock your rig.
I love the dock, but the collar needs to be reworked. I had a friend do up a CAD of the modified dock and wanted to see if anyone was interested in going in on a batch order. That would help bring down the cost close to nothing. So if you have the Gorelock 2 for an Ultra 2 or Ultra 2c (Clipper 3 and Phantom), then you should have this collar.
So a batch order of 20 would cost less than $50... who's in