You will need a short adapter cable (C NET I think but check) to go from SeatalkNG to the Element 9, only a few dollars. I think you have the T connect for the Element 9 the wrong way round as the feed needs to be a spur on the T and an extra blue end plug
fitted. These blue plugs are essential at the ends, but the black plugs for the spur fittings are just dust caps btw.
I am having discussions with Raymarine at the moment because the depth
informatin from my ST60s doesn't show on my Element 9. The wind
and speed does. You might have better luck with 50i because ST60s need to use the Seatalk/SeatalkNG converter to talk with SeatalkNG. Note I may add a sounder directly to the Element 9 later, but for now it would be nice just to have the sailing display display working with a depth reading.
You have a VHF
with Rx only. Since you have a spare spur socket there, why not go for an AIS
that also transmits, budget
Is the power supply into the network close to the batteries
? Why not put the power into the network using a spare spur that the VHF
Do you have an authpilot on board?