I would recommend you mount the Point1 at the transom as close as possible to your transducers. The closer it is to the transducers the more accurate you will be when marking waypoints. It's a good idea to use a compass in the area you want to mount it to check for magnetic interference. Just move the compass around the area and watch for any deflection of the needle. It's not a bad idea to mount it with double sided tape until you know there's no interference while the motors running.

If you fish offshore structure it's worth it's weight in gold. You'll be able to fish waypoints without the map spinning around when you drift in the wind or current.

The great thing about a Point1 is the heading sensor. I set up my console unit to use the Point1 for GPS and heading and the bow unit is set to use its internal antenna for GPS and the Point1 for heading only.