Dave, My inverters are factory wired to allow for powering 2 rings each. Not sure about yours. One relay per side should due. I don't recall the amp size of the relays. I do recall that the supply wiring to the inverters is really small telling me they can't draw a large amount. A 20/30 relay has worked fine for me over the years. The relay I use has a mounting tab on them. You can mount the relay or if out of sight, wire tye it to the loom. Wiring the supply (+) side of inverters to #87 of the relays should be just fine.

James