I installed one from Dakota Digital in my Syncro Westy with a Subaru 2.5
engine.  In the engine bay.  It worked perfectly with the "reversed"
accel cable setup.  So I can't say how to hook it up there with a
waterboxer.

The GoWesty setup seems slick to me--no running wires from back to
front.  The only thing I don't understand is how they get a brake
signal.  In the rear, you can pick up a brake light wire to get it.

The Dakota Digital is a Rostra.  I love it.

Richard