It really depends on what sonar you want to use when you are fishing at the bow. As others have stated; the 2D sonar (200/83kHz) from the US2 will work but you will not have any Si/Di sonar unless you mount an Si transducer up front as well.

It also depend on how you are going to mount the unit at the bow. By using a mount system like a RAM mount you could buy two mount bases for it and not have to buy the Humminbird GM-2 Gimbal Mount.

Let me know how you want to proceed and I can get you a parts list of what you will need.