I am going to install 2 new units, one with gps in my boat.  I think I am going to go with this "backbone" setup.  I understand the basics of it, but I am not sure if I still need 2 transducers or not.  Can my units share one?   I am also putting in a temp sensor, and possibly a fuel sensor as well.  I hope these work as good as they claim to.  

From what I'm hearing they (lowrance) have been having major issue's with the temp guage/sending units using the backbone setup's? So much so that they can't get the temps to read on the graph...

You may look further into it before you invest.

I don't have that setup personally, it is just what I have heard.

i do not have the fuel sensor, but i do have the temp sensor and i have had no problem yet. and yes you can put two graphs on one xducer and on one gps module, by use the T connectors

i have the fuel sensor and it is very accurate.

if you want to share actual graph display, the lowrance-net will not do that, but they will share digital depth readings. if you want to "share" a ducer and get actual graph type readings you will have to get a switch to change back and forth from each graph.