Brian,
sorry I can't help you with the handbrake cable, that's one of the few things I haven't had to tinker with yet.
I'm interested in the approach you're using with respect to a rear disc brake conversion. It wouldn't by any chance be the one documented on the GGLC web site, would it? This is the one using Merker calipers.
(I was all hot to do this myself until I got sidetracked with my engine noise, which led to a rebuilt pump, a valve job, porting, and higher lift cams, valve springs, followers etc. A Europa is the dictionary definition of mission creep.)
Regards
Rick