RK07 Manual Dual Port?

After seeing an M7706 on eBay (and realizing I already have a spare), but no dual-port card (M7730), and reading instructions in the maintenance manual regarding placement of a single M7706 drive interface card in either slot, depending upon whether A or B is selected I began to wonder... Is there any reason one cannot do a manual dual port on an RK07 by having both M7706 slots populated, but then only ever selecting A or B using the buttons on the RK07? Has anyone ever done that? The existence of two separate wire list pages in the schematic, and a quick look at the M7706 diagram output signals suggests that this would *not* work - that the output lines of the two M7706 cards are wired together on a single-port drive and driven by ordinary TTL, and that a dual-port drive had different wiring on the backplane, even though the card cages are the same and the backplane itself is the same. JRJ