I've got a very similar problem.
SSBC front disc conversion, 10" rr drums
My MC, prop valve, and set-up is the same as your Wilwood.
Does your pedal return properly? Mine doesn't. My story is long and complicated, but something I noticed is after I pull the drums and do anything with the rear brakes, the next time I drive it, the pedal returns properly for the first several stops. Then the pedal starts to stick again. I've pulled the MC apart, checked the pushrod length, checked for mechanical binding, etc.
Something is going on with the rear brakes. I think we need to better understand the residual valve(s) in the system. The SSBC rep has been very helpful. I'll let you know if I learn anything new.