I got a Jobu-Jr (original) Gimbal head for my tripod this week (it was a good week on ebay lol).
Regularly priced at $299 +$50 for a lens plate USD, it was on sale as they have changed the design a bit and were clearing out the old stock, for $150 USD + $50 for a lens plate.
Here's their image of the mount. I took a few of my camera sitting on it but I am running out the door to field test it. So far off the back deck it has been an amazing tool. To ba able to reduce the shutter speed on the camera to 1/60 with the camera zoomed out at 500 and not have camera shake is a HUGE bonus. The speed and agility of this mount are simply amazing. It holds the balance of the lens so that when you let go of the camera it stays put. No matter if I have it zoomed back to 50 or all the way out to 500.
Here's their shots of it. Look for more later today when I get back home.
Jay