I too have been debating the depth finder issue and some of the guys on our lake have opted for the $99.00 version from West Marine, about 2 inch round face, dont know the Model number, two of them say they get very erratic readings at times and not always while undersail.
I am considering one of the GPS/fishfinder combos. The Idea of mounting it on a swing away mount is a great idea, use it while under way, and inside for anchor alarm etc. will overnighting. can you supply pics of the swing arm?
I overheard a conversation in a local store that Lawarnce was having antenna issues with their HD gps/finder series, any word on that?