Duane, I'm using the swivel mount attached to the bottom of the 478. This way it is easily removable. How is your's mounted? ( no banana jokes)
There you again, "opening the door"

I am using the Garmin supplied "marine mount". The difference with the marine mount is the locking button on the release tab. Aside from disconnecting the power cable, audio out and XM antenna, it pops right off. On long trips (eg MV) I had the antenna held down with one screw. It would still bounce around on the bracket occasionally without the screw.
I haven't contacted Garmin yet, but my power cord broke on the last day coming home from MV. That is the 3rd broken cord. Still have to contact them about the screen, you can see all the scratches in the above picture.
If you look at the "back side" picture (honest, I wasn't thinking of what you might think of that

)
you are looking at the accessory mount part of a Techmount bracket. I have an older version, but it looks almost the same.
http://www.techmounts.com/products/index.php?page_function=detail&product_id=69I am using the shortest arm. This is allowing for a very "tight" install on the bars, the GPS is below the top of the fairing, and positioned just about right for my line of sight. I don't like the swivel mount, too tall, bulky looking, and looks like a BMW-GW install. And the Techmount IS show chromed

When I changed the bars to the Wild One's I needed a new handlebar clamp - I called Techmount (after a week or 2 of un-returned emails) and the person I spoke with told me the mounts changed, new ones will not fit older arm and plate assembly. He told me he would look around for some older stock. 5 days later I had the parts I needed, no charge.
BTW, I am about ready to turn the weather subscription off. Don't need it for now, the weather will pretty much look like this all the time until March.