I have a side imaging+down imaging transducer on the stern for the console unit, and then a down imaging transducer on the bow built into the trolling motor for the bow unit.
You're right that side imaging requires a forward motion. It would be nice to have it on the bow too, but unless you're willing to install a transducer bracket like the Da' Ducer Apparatus from Podunk Ideas, then I wouldn't mess with it on the bow....use the savings to get a bigger unit at the console.