Cut a piece of cardboard to the size of the unit you're interested in and use it as a guide. Different mounts are available that take up some space to the sides of the MFD, some mount behind the unit completely. I don't recommend mounting MFD's into any console, they are not adjustable for better viewing and are a theft problem. I have my HDS 12 mounted just below my line of sight because above 60MPH I need to navigate, them bouys, they are pretty hard to see in time to avoid shallow areas in reservoirs.