The BF guys told me that a standard (26") rack would fit the Llama just fine. I will bring a Moose rack along just to be sure. Not too interested in any of the seat post mounted versions -- Burley's is a far superior, more stable design. We have Moose racks installed on 3 bikes, so we're pretty committed to it.

Disc braking puts quite a bit more bending force on the fork legs than rim braking, and the fork needs to be designed for it (i.e. beefier tubing in most cases). A decade ago when a lot of mountain bikers were trying to figure out how to retrofit their rigs for discs, there were a number of failures of forks that had had disc tabs welded on. When I'm descending out of the West Hills at 35mph every evening, my life depends on my fork, stem and handlebars. I take no chances with those parts.

I'll ask Bike Friday and HPM about their disc options and confirm that their forks are specifically designed for disc use. If not, I can always get a custom fork made to my exact specifications for $250. Combined with the Xootr frame (assuming I'm willing to give up the rear disc -- gotta do some thinking about that) it wouldn't be a terribly expensive route to go.