If you want to use the HDS-7 at both locations, all you need is a trolling motor transducer at the bow, and another power cord. Then an extra Ethernet cable from the console to the bow if you want SS/DS at the bow..
The LSS-2 is an Ethernet accessory so you can put the LSS box under the dash, and have SS at the bow or console.
The easiest method of moving the display is by using a RAM mount so you don't have to unscrew and detach the gimbal mount.each time. I would just take an extra RAM mount ball at the bow.