I have a Gitzo 3541 - it is a model without a center column. The lack of a center column is important, as that will allow you to get way down to ground level.
I also use a Wimberley. Some folks have complained that a Wimberley will not allow you to get down low enough, but I have found that by inverting the vertical shaft and re-attaching the mounting plate, you can hang the lens from the plate via the lens foot (as opposed to setting it upon the plate). This lets you get way down there - just a couple inches above the ground. Any lower than that, and your foreground will just be a bunch of out-of-focus mush . . . and not very aesthetically pleasing mush, at that.
The technique I've described - inverting the vertical shaft and reversing the mounting plate, may sound like it'd be a hassle, but I do it many times a day, and it only takes me about 6 or 7 seconds to do it.
I am shooting with a large supertelephoto, similar to yours, so I am familiar with the support needed for large, heavy lenses, and the Gitzo/Wimberley function very nicely. Well, except for the fact that one of the legs has fallen off the Gitzo. Only 4 years old, too. You may want to go with tripod legs from Really Right Stuff instead of Gitzo - they have a reputation for higher quality and superior customer service. You really don't want legs falling off of your tripod - it sucks when that happens!
"Your" and "you're" are different words with completely different meanings - please use the correct one.
"They're", "their", and "there" are different words with completely different meanings - please use the correct one.
"Fare" and "fair" are different words with completely different meanings - please use the correct one. The proper expression is "moot point", NOT "mute point".