Did you try the mod at VR6 Matt. Look at the last pic I posted. Shows a trace being broken at VR6 and then being placed there. You could add your variable power there couldn't you? Be like adding the resistor there but your variable instead. I could be wrong so look into this more before you dive in. Hope you find a way to add it. Be safe and have fun. That is what its all about!! And keep it clean and mean!!