Don't have a ryca but for my taillight wiring I welded a small bolt to the bottom of the metal tail I made and used insulated wire clamps held with washers and nuts  to hold the wires.  You could do the same by fiber-glassing a bolt or something to the bottom of your tail and pan.  I used two clamps to span about 14 inches.

On the trike I built, under the rear fenders I ran some of the split plastic wire loom you can get at NAPA.  I taped it in place then fiberglassed over it. I ended up with a fiberglass tunnel to run my wires through. You could use light plastic tube etc. For a larger one I used a piece of garden hose that I waxed with car paste wax then pulled out after the fiberglass hardened.  Carl