I had a couple of people ask me to comment on how I like my installation of the HDS-10, HDS-7 on the bow and HDS-5 in the console and networked with the structure scan. The 10 has an X-ducer, the 7 is using the TM's built in X-ducer and the 5 does not have an X-ducer) I'm by no means an expert and there is a lot I'm sure I'm not doing right but here's what I've found so far.

The 10 mounted on a swivel mount and 5 in the dash make a very good pair networked together. There are times when it's better having the sonar on the 5 and using the 10 for mapping. This worked great when running a strange lake (Lake Falcon) and when getting way back into the creeks. The size of the screen on the 10 lets you zoom in close enough for good detail (using Navionics HotMaps Platinum) and still see what's around you.

What didn't work was having the bow mounted 7 networked with the other two. I finally pulled the network cable out of it so I could use it as a stand alone unit. When networked, they all use one unit as the source and the others read from that source. That created more problems than it was worth when trying to use the X-ducer at the front to see what was under me while on the bow. As mentioned, I finally pulled the network cable out of the seven and just used it stand alone. Doing this I never picked up any interferience between the front and back units but we never fishing any water below 20 feet. What was draw back from pulling the network cable was I couldn't get the waypoints I had marked and stored in the 10. What we were having to do is go to and find the things we wanted on the 10 and then mark them again in the seven. Then use the seven to manuver the TM in position and mark them in the TM so it could hold us or manuver between them. Kind of a round about way of having to do things from the front.

Now, there may be ways around this but I'm not familiar enough with them to know it yet.

Contrary to what they say, when you have units networked together, there is a lot of crap to learn and things are not as simple as they claim.

As for the structure scan and down scan, it's amazing.

What you are referring to is "network sonar", that is the sharing of one transducer with all units linked via the yellow Ethernet cable. I really like this feature. To cycle between sonar sources, from the sonar menu select sonar source (either "local" or "other unit model name") from the bottom of the menu. This is a really neat feature that eliminates crosstalk between ducers, as only one ducer functions at a time. Before, you had to "stop chart" on one unit to prevent crosstalk. This is also beneficial for your back seat partners, as they can now watch the sonar without causing any interference. That's good that you weren't getting any crosstalk with your system when running more than one ducer at a time, but I would suggest that is the exception rather than the rule, especially when running the sens. at higher levels.

To disable network sonar, instead of unhooking the Ethernet cable (which as you point out you loose waypoint sharing), just deselect "network sonar" under the sonar menu on your HDS 7. The other two units will still share sonar until you deselect those.

another option is to network the units via NMEA 2000 to share the waypoints.  This option is more complicated than turning the network sonar option off.

I use a switch to change my ducers because I want the guest to see the same as I be it front or back.

Regarding Ethernet vs. NMEA 2000 and wpt sharing, Ethernet is the way to go.  NMEA 2000 networking will only share new wpts, and only if both units are powered up.  With Ethernet-linking, you get "complete" wpt sharing.  That is, all wpt changes are saved to each Ethernet-linked unit (new wpts, deleted wpts, name/symbol changes, etc.), whether all units are powered or not.