Grip heaters

[Brian VT]

I've got my grips and switch installed. I'm trying to decide where to take the power from and where to ground. I've got the euro bike with the larger stator. I'd rather not give up my headlight.
There's a yellow wire with an appropriate blade clip that goes into a box next to my horn. Can I just plug this into my heater switch instead ? If that won't work, how about tapping into the wires for the little "running light" next to the headlight ? For the ground I'm thinking about drilling into my top triple clamp and running a screw in ?