Dave,
I installed a Raymarine C80 chart plotter last year. I bought the entire package including radome, plotter, and cable as new old stock for $1500 off of EBAY. I wanted to make sure that the system would be compatible with the raymarine instruments and auto pilot that were already installed. I also had to purchase a 125 GPS antenna. I flush mounted the chartplotter on my 343's helm pod. Be careful, because the newer wide screen models won't fit if you want to flush mount. The radome is still in the box and uninstalled. Definitely thinking about a stern pole mount to simplify installation and maintenance in the future. Also plan to install a lift on the pole to make hoisting the outboard of the dinghy easier. Mast mounted radome is nice; however, I don't want to incur the additional expense of lifting the mast to facilitate installation.