Does anyone have an opinion on this depth finder? I'm trying to find something to put on my towee with gps and down imaging. The online reviews are mixed. I know most flats fishermen don't need the fish finding feature but I fish lakes and rivers more than salt. The raymarine dragonfly seems to come with better maps but will cost me more unless I get a 4 inch screen. I'm afraid that might be too small. Does anyone have any recommendations or other models to check?