Some time ago I posted a topic about a contraption for lens support here - http://www.uglyhedgehog.com/t-183287-1.html - which I have since named "bodypod" .

Due to the proliferation of 150-600mm zooms I thought I should devote a topic to the support and stabilisation of these types of lenses. Having used a 300 2.8 W/2X and 100-300 f4 W/1.4X for the last 3 years has given me some valuable insights into managing bigger lenses - especially for fast action wildlife and sports.

Below is a an image of the main component parts of the bodypod which I have field tested at Viera - but would also be very effective at Circle B -or- anywhere for that matter. It is especially useful for BIF and is the next best thing to handholding IMHO.
1. On the left is the adapted painter's pole which adjusts from the top for ergonomics and speed. You could use a standard monopod here - if it would collapse short enough. But for birds, sometimes you need to go up high with the adjustment - in a hurry ! This pole has a Manfrotto 234rc tilt head on it. Not, shown here, but I recommend using a macro lens slide on the lense's tripod collar to adjust for proper balance. The 234rc can also be adapted for arca swiss mounting.
2. At the top are heavy duty workman's suspenders. These clip onto the fishing pole fighting belt to help distribute some weight to your shoulders and upper torso. They are not the latest fashion craze - and you can get away without using the suspenders - but once you try them you will really appreciate what they do ! - (especially for older/weaker people). Using the suspenders also extends the amount of time with which you can effectively obtain good images.
3. On the right is fish fighting belt - this one is hard plastic, but there are many varieties to chose from - but they must have a two slots in the front for the suspenders to clip into. Some varieties are all metal. If you are older/weaker, I recommend wearing a lower back elastic support of some kind under this belt.
4. At the bottom is the tethering strap worn around the neck and under one arm for insurance/safety and to allow hands free operations if needed.

The second image shows the upper "facial stabiliser" that is used in the accessory (flash) shoe on the top of the camera where the forehead is used to keep your face off the back of the camera and help stabilise the camera/lens. I do recommend the stabiliser be used with an eyepiece extension. This stabiliser is used in concert with the bodypod - but is also effective in handholding all lenses! There is also a lower stabiliser that can be held in the tripod socket of the camera to fit your chin.

None of this stuff is available commercially !