To bad, you're probably going to have to 'compromise' on a
BH-55. I just ordered one this afternoon, so I can tell you how smooth it can pan/bob/twist/turn/roll ... in a couple of weeks from personal experience. Besides the large ball, quality machining, and rave reviews, it also has numerical settings for friction. That looks quite useful to reset certain characteristics that worked out in practice. I'm not sure how it would be affected by salt water chrystals though.
Well, the package arrived yesterday! Shipping took a bit longer because another item that I also ordered was temporarily out of stock. As expected, the BH-55 is very well machined, handles quite nicely, and as a bonus it also looks very nice.
The large diameter ball allows to apply a lot of friction, so I'm confident it can easily carry larger loads (it's rated to carry up to 23Kg) than I currently have available. The adjustable friction works fine when swiveling the gear around handheld, although for a heavy camera/lens one needs to almost apply maximum friction if you want to prevent it from accidentally tipping over when you let go of it in a non vertical position.
In that particular maximum friction position it becomes slightly jerky if you want to pan around. That will improve with use, according to the (A note about break-in) accompanying paper. For normal use it is
not recommended to lubricate the ball (because that would retain dirt), but for Nicolas' particular case it might even help (adds a silky smoothness to movements and protects against sea water). The head comes internally lubricated and the parts that need lubrication are (O-ring) sealed. Mud or salt water should be lightly rinsed off with (not submerged in) fresh water.
Of course the camera/lens combo should be mounted at a gravity balanced position, because any ballhead, almost by definition, provides an unstabilized platform. The closer the mounting point is to the camera/lens center of gravity, the smaller the force arm.
Use on a monopod almost seems like overkill (although Nicolas' shooting requirements are different from say a field sports photographer's), but the Arca style of mounting plate at least prevents the camera from rotating loose from its mount, e.g. when carrying it on your shoulder.
For regular tripod work it is a dream tool, with only a modest height (keeps center of gravity low) and a big grippy main lock-knob that locks firmly and
it doesn't change camera position when you tighten the lock. I mounted a Panning Clamp to the ball, which is
very useful for a good level panoramic setup. It can also be fitted (either by RRS or the user) with a quick release clamp, which works good and can be useful when camera bodies need to be swapped frequently.
There is one important warning sticker on the ballhead, that warns against mounting on the treaded stud on top of the tripod if it has more than 5 threads above the platform. My Gitzo was fine with 5 threads.
Bart
