My guitars always have the same binding scheme, with 5 purfling lines on the top and two on the back and sides, so I made three binding cutters with permanantly set guides, and modified my Ribbecke binding router to accept them.
Each cutter consists of a Porter-Cable 310 laminate trimmer with a 1/4" bit attached to a plexiglas base. I made one for cutting the binding ledges, one for the top purfling and one for the back purfling.
I machined 1/4" aluminum stock to create the guides and bolted them down with 1/4" machine screws. I drilled holes in the guides to allow access to the laminate trimmer's mounting screws so I can remove the laminate trimmer and change the bit without disturbing the guides.
The carriage has a slot to accept the plexiglas bases, which simply slide in and out to change cutters. I made the slot a pretty tight fit, and since I'm pushing against the guides as I rout the ledges, the bases stay put quite well.
This system allows me to cut both ledges of a top or back without readjusting the body carriage to flip the guitar over. It only takes a few seconds to switch cutters, so the system saves a lot of time.