Mike,
Stock for now. The more I researched the shaft upgrades, the more compromises I find. I will be looking at all the options again once back from Asia
Fortunately, Rover made these shafts easy to swap out. I also had an interesting discussion with one of the Camel Trophy organizers some time ago, and they experimented with several shaft types and ultimately decided to stick with stock, as they were easy to swap and served as a fuseable link (saving the more expensive and more difficult to change differentials, etc.) Just another perspective I found interesting.
Well, the stock diffs are weak as can be. Now that you put the ARBs, in the rear axle shafts will be the next weakest link, like you mentioned. The problem is that they are really, really weak compared to the rest of the drivetrain and you will be changing a lot of axle shafts if you lock the ARB. My brother snapped a rear shaft literally 2 miles after installing his Detroit. One little dirt ledge where the bulk of weight of the vehicle was on one side of the rear and pop.
With my 235s / rear DT w/ GBR shafts / front TT & stock shafts/cvs, I've been fine for years, even with some less than perfect driving on slickrock. I know that I'm on borrowed time, but I keep spares, just in case.
I'm not sure if Thom dislikes Right Stuff for sealing the thirds, but that's what I just used when swapping thirds from my silver Disco to my XD. We'll see how well it holds.