Electronics Rigging/Addition Questions

I currently own a 1890 Pro V tiller. With the rear electronics box. Currently I have a Lowrance 104 (which
I like) for my depth etc. I use the 104 full screen. Currently,for the the GPS/map only I am using a LCX 28 with external ant. The 28 is the unit I pulled from the bow location as I also have the bow rigged with GPS ant and a Terrova bow mount with transducer and power cable. Also I have a bracket mounted to the rear instrument storage area that at one time held a 350A which I sold. Here is what I am thinking, moving the Lowrance 28 back up to the bow for those times I fish from the bow pitching jigs or using bottom bouncers it would be fully GPS capable with maps and depth. Then purchasing a 520 with a external ant for GPS only and placing it next to the 104 like the 28 was. I realize a smaller screen, could be a draw back. then purchasing a HD5X with structure scan and use it only to scan structure not GPS capable. My reason for the 520 is it has a external ant, units with internal ant won't work in the electronics storage area. I find my 104 works best without the GPS split as I noticed prefered faster chart speeds. Do any of you have any better suggestions or ideas. I am thinking the HDS5 for structure scanning only the screen would be large enough to accomplsih this. Do you see any major obstacles with this set up. thanks in advance