Thanks to all for the info and recommendations. I finished the hardwire installation for the Nuvi 550 on my 2006 Ultra. I used a Ram mount and bought the hardwire harness to wire it to the spade connections behind the headlight. All went as expected and it works great. The only unsightly thing is the fuse holder that's part of the hardwire harness. I wanted to be able to access it without removing the fairing so I ziptied it to the Ram mount. It looks a little funky but it works so it'll have to do for now.

 

You can still relocate that nicely so it's under the fairing yet accessable if you position it so when you look under the fairing by the forks it's still accessable for a fuse swap.