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I think I found a heavy duty answer. Siri p424x monopod and manfrotto MH055m8 video head. More money, but less than big pro rigs...
If you can find the one I linked to in a shop to try, its worth checking out. I've used it with a fully kitted out Sony FS100, which weighed about 7 or 8 pounds and it was fine. Definitely at the top end of that head's capacity, but I haven't had any issues. I used it with a 5d2 and 70-200/2.8 as well, no problems.