Discovered today my old Shimano Ultegra RD-6600 rear derailleur works fine with a SRAM PG-1070 11-32t cassette.
The B-screw is about 3/4 turned in, shifting is nice and smooth. Cheap 10 speed low gearing setup for CX or steep gravel roads.
(I couldn't get it to work on my Ultegra 6700 bike though, the cage looks slightly shorter)
Skye