I wonder, also. I'd really like to ride a bike with this installation to see how the geometry works. The impression I got was that the offset was selected to create the right trail on a Monolever when the front is higher but the rear isn't.
I don't want to raise the front much at all. Looking at the forks I have,it seems that I'll end up a bit higher just due to the position of the clamping areas, which is OK, but I want to limit that as much as possible.
Interestingly enough, the KTM triples (from the EXC at least) have very little offset, meaning more trail. In fact, the R100GS has less trail (100mm) than any comparable bike, which I suspect is why there is so much kickback when you hit rocks sideways. I'm not in love with the BMW geometry so I see no need to duplicate it for handling's sake. OTOH, of course, I do appreciate the greater steering lock that comes with more offset, but you have to compromise somewhere.
So, the new group buy is tempting, but I'd like some sort of indication that the offset is appropriate for my particular needs. I'll have to sift through the details more, but in the meantime I'd like to see some feedback from the existing user base.