I used a 1" Ram mount with a U bolt mount onto my right handle bar.
RAM 1" Diameter Ball Standard Length Double Socket Arm with Zinc Coated U-Bolt Rail Base
Product Number: RAM-B-149Z-QU1U
That way I didn't have to drill holes in the dash and it rides pretty firm.
It also makes it easy to remove my GPS unit and put it back on mh boat.
I run the power cord right off of the battery with inline fuses so that when I turn the sled off, the power doesn't stop and I lose my GPS coordinates.