Due to highly unusual terrain, I have a 400 amp service with 2-200 amp disconnects mounted a considerable distance (175') away from a house and a separate Casita. Each 200 amp breaker is going to serve feeders that run to a sub panel at each building. I have installed GEC in the form of a UFER in each slab. There is no metallic path to either panel due to the feeders being buried in PVC conduit. Since these will be sub panels, the neutral has to be isolated and insulated form the panel. Do I run triplex or do I need to run a Quadraplex since each building has its own GEC UFER? I believe I have to run Quadraplex to isolate the bonds from the neutrals. The inspector says I should run triplex due to the existence of a UFER at each sub panel. Any recommendations?