This gallery illustrates that the Wimberly WH-200 can be used with a Nikon D200 + 70-200 VR or 300/4 AFS, with or without TC's, and maintain optimum balance and swing fully through vertical. This cannot be done with a Sidekick without tilting the Sidekick back, as illustrated in teh D2H gallery.
Potential Problems:
1) Both lenses were not fully engaged in the clamps when a TC was installed. This was more of a problem with the TC20 because it is longer, forcing the body further forward to achieve balance.
2) Conversely, without a TC, clearance between the body and the gimbal clamp is somewhat limited. I was able to achieve optimum balance, but it was tight enough to note here that a slightly difference configuration resulting in a different balance could have a different outcome.
While all images here were taken with the package at optimum balance, if you experience different results you can unbalance it to achieve necessary clearances. Depending on how you do that, your gear could be endangered by a sudden drop, depending on what you need to do. Hopefully my results are representative of these basic configurations.