I built a capacitor pack for my XL out of off the shelf capacitors ar radio shack. I bought three 2700 mf capacitors. (the biggest ones they had) Soldered them together in parallel on a circuit board I bought there too.
Put it in my XL, changed all my instrument lights and taillight to LED. When I kill the engine the neutral light will stay on for about 15 seconds on reserved power. Turn signals, horn and lights all work great when running. Heated grips too.