Last year we went to Yellowstone in the spring and rented a 600 f/4. Accepting the fact that a long lens was somewhere in my future, I bought a Realy Right Stuff (RRS) "TVC-33 Pano-Gimbal Package". All RRS gear is very well made in the US, it has very smooth action, and is a little lighter than a Gitzo/Wimberley combination. This package is somewhat expensive at $1,861. You can cut that back a bit by side mounting your lens without the vertical arm and skipping the leveling base. You do not use a ball head with it. I tried a TC2 on the 600mm and it was to laugh. At 1200mm the atmosphere blurred anything at any distance and my long lens technique proved to really suck. It made a good telescope to watch a wolf trying to get at a bison calf and the bison forming circle all at about a mile away. Photos show some hazy blobs. I’m still working on my technique with a 300mm f/2.8 sometimes with the TC2. Got some great shots of snowy owls this winter with the setup below. That’s me hauling the rig around the estuary after extracting myself from being up to my knees in muck. The gear remained unharmed, my ego suffered.
If you decide to use the leveling base, consider the “Leveling Base HDL with Hook”. You can use the hook to add stabilizing weight to the tripod plus the shank is a little longer which makes adjusting the base a bit easier. Also, while you’re there maxing out you plastic, take a look at the “Long lens support package”. It is not a substitute for the long lens technique described elsewhere here but it helps.
Their site has a lot of excellent advice: see “Be a Gear Expert” and “Videos”.
Me just out of the bog. Photo by laughing wife.
RRS gimbal head, long lens support, D300 with a TC2.