the previous model delorme gps i have doesnt have the connector at the gps level (just has a wire coming out). if you want to mount it outside, all you need is a good dose of sealant around the cracks and your good to go. my friend did that for years with his old delorme gps, and that as back in '99.
not sure how hard it would be to seal the new ones though, connector makes it just a tad harder.
dont like the bright yellow color? spraypaint it!
did I hear correctly that some people mounted their GPS hidden under the dash with no problems? Sounding like a good place to put my new one. not worried about theft, just beats the hell out of the roof