I currently have an old rack bodged to clear my BB7's on my uncle john. My tempory bodge has lasted 2 years ... but won't last much longer
I'd always intended to buy a Topeak Super Tourist disc:
... which has pronounced stubs to clear the disc caliper.
I've also noticed other, purportedly disc compatible, racks. These don't seem to have the pronounced stubs, but are a) cheaper and b) slightly less like the forth rail bridge.
How do they manage to clear the caliper?
Madison Ridge Disc Pannier Rack
(There is also the new-ish 'Topeak Explorer 29er MTX Rack', which looks OK and uses the same stubs as the super tourist)