Frozen red clay.
To answer my own question.
Aside from that, the rear end worked perfectly. The shock bracing combined with a properly valved and sprung (21kg/mm Ohlins spring) works really well, My wife reports no savage jolts transmitted to her back (she has a pinched nerve from a car accident and is sensitive) and I don't recall the ABS kicking in on the rear once in the whole fire trail experience (about 250kms of dirt roads, fire trails, and 4x4 tracks). I think I bottomed it a couple of times, but the suspension guy has it valved such that it comes up on the bump stop more gradually and without the nasty "crack" it used to do.
Front end.....well.....considering...I suppose....yeah...no.
It almost works.
The problem here is, to make it work is going to cost a lot more money. A lot more. The rear end has totalled about $2400 to get to where it is. Able to do fire trails with a pillion and a full load of camping gear.
I started with the standard Ohlins solution for the F800, then went from the 17kg/mm spring to a 19....then to a 21 with a full revalve. Along the way, bent a couple of shock bolts, started to damage the frame mounts, then used the info from here to combine a Rally Moto brace with the Indy kit. Then change it a little with alloy spacers etc.
In hindsight, if I was setting one up for a RTW trip, I'd start with the complete revalve and the 21kg/mm spring - for a solo fully loaded trip. It's the wrong bike for a pillion RTW trip. But for exploring all the local National Parks and State Forests with a pillion, it's working very well.
I personally think that BMW needs to rethink the rear shock mounts. Not drastically, just minor modifications. It would make the whole process so much easier for so many owners. Rather than just having the owners give up and lower their expectations.