I've used a B1 with 8X10 stuff for the four last years. I used it under a 7X17 Korona, it was not very comfortable without the camera's rear rail, the head being very off-centered, but not so difficult. With a 305 or a 360, the longer lenses one can use without the extension, the Arca, even completely off centered didn't fail without having to support the front of the camera. It's also a pleasure to carry a head without levers, and I have found I could set more precisely the camera holding it directly without levers.
I received a 7x17 Canham three months ago and have been lucky to find a good used Arca B2 at reasonable price : it's a dream to use. The camera is now well centered on the head, of course that makes the setting much easier. The separate axis, the ability to set independantly the tension on each axis make the thing really easy to use, and I always can move freely the camera to search on the GG as I like to do. It's heavier, but I don't walk miles and miles with the camera, so this is not really an issue. The too small panning knob locks easier and stronger than on the small sister. I would like the smaller ball knob with a better grip or another design to help good locking.
I like very much the B1 with 8w10 and smaller stuff, it was strong enough for the 7x17, but in this larger format I felt, maybe because of the width of the camera and amplification of the least movement, a bit more difficult to level it so quickly and precisely. The B2 solved that.