It is not possible to put one mfd on one card and the second mfd on the other card.
I know DickDastardly was successful with using MaxiVista, to export the MFD data to another PC's adapter.
MaxiVista allows for multiple PCs/laptops to be networked together to provide extra desktop space.
It can be setup to have more than one display spanned together, as a single secondary...where the primary PC thinks that all of them are just one secondary display.
So, theoretically couldn't you....
Setup the primary PC...configure two displays on the 2nd PC to span via MaxiVista...export the MFDs to what it thinks is a single secondary display...then just alter the positions of the MFDs, to get them where you want on the two secondary displays???