Hi there, I had a similar challenge when putting in a multi-tap OT (4/8/16).
To make life easy for me, I wanted 3 jack sockets on the rear, where whatever speaker was being used, could simply plug into the relevant socket, with no switches to flick. The NFB loop caused the problems.
I sorted it by using switched jack sockets that “made” a seperate connection when the jack plug was inserted, thus utilising the NFB, but only on the relevant OT tap. Works fine.