This is just some info.theres no guarantee of being interference free.
I think that you said you were going to one control head and a 360 right.the 360 runs on 455kHz and while the 360 is running ,the software in your unit shuts the pinging off to your si,which is 455/800.all thats left pinging would be your 200/83 2d and the 455 on the 360.there shouldn't be any interference (imo) between the two.
If you have a bow mount 360,there an option to stop pinging while not using.if you have a transom mount 360,when you retract it the pinging stops automatically. Maybe you could call humminbird and verify with them to make sure,but thats the way that it should work