I managed to install yet another graphic card into my computer (I had to put out the sound card for this!). D3D9 allows two full-screen windows on two devices, that's a good news. The bad news - I doubt additional "software" videocard is D3D9 compatible, thus it cannot be used in the process.
So, that's a question - why do you use additional computer to show MFDs? Is it possible to use direct connection between the main computer and MFD video display? The only other way to solve that Mirror Pro limitation is usage of GDI to draw the MFD window, and it's exactly not full-screen (but may look very alike). Another suggestion is usage of EECH specific send/receive programs (and not to use Mirror Pro).
_For now_ I see the following limits of _current_ (now + 2 days) Direct3D9 implementation for EECH:
0. All windows are drawn via Direct3D9.
1. EECH main screen
1.1. In full-screen mode it occupies only one display.
1.2. In windowed mode it may be stretched upon several displays of a single graphic adapter or multiple ones (tested a bit).
2. MFD screen
2.1. In EECH main screen windowed mode it's windowed too. Maybe stretched and moved within displays of that adapter. It may be the same adapter EECH main window has or another one.
2.2. In EECH main screen full screen mode
2.3. If EECH main screen and MFD screen use displays attached to the same graphic card.
2.3.1. If there are only two displays attached to that graphic card are part of "extended desktop" (there are no others, or they don't "extend desktop") MFD window is in full screen mode.
2.3.2. If there are more displays - well, there are variants. Either it is windowed, or others displays are turning blank, or one display - one MFD, or... or just exit with error.
2.4. If EECH main screen and MFD screen use displays attached different graphic cards.
2.4.1. Exactly one (selected) display of each of those cards become full screen, MFD window is full screen. Other displays attached to those graphic cards continue to show what they had on them before.
3. As far as I understand (and it may be wrong) several adapters in SLI/Crossfire mode are a single graphic adapter.
4. NVidia Surround and AMD Eyefinity may (again it may be wrong) extend EECH main window (or MFD window) on all displays attached to a single graphic card.
4.1. I believe there is a software way to make the same they do and it must be implemented inside the game (not tested yet).
4.2. SoftTH allows to do this without in-game code and can use several different adapters simultaneously. For some games.
So... I address you - the users of multimonitor configurations. Do the limits above suit your needs? It's better to answer this weekend. Or this week.
If you don't answer I'll do what suit my needs.
FireBird