I took another look at the Mac Plus and it seems like the Mezzanine Slot Hack will leave the SE/30's PDS untouched . . .

. . . if it will work at all. It appears as though the Mezzanine Card will need to be mounted just a tad above the top of the PDS EuroDIN Connector. SolderTail Machine Pins replacing the PDS Card's Connector will do the job of raising the level of the card vertically and conserving vertical expansion space at the same time.