I did get it to work I thought with switchresx, but somehow it seemed instable. Not sure what went wrong yet I have to do more tests.
Meanwhile I got this reply from Matrox:
The DualHead2Go Analog Edition is only compatible with computers that have a VGA output port that is native to the body of the computer. No adapters are to be used at the input of the Matrox GXM product line as they create bottlenecks limiting the required bandwidth. This will result in limited to no output resolution. The DualHead2Go Analog only has 2 available resolutions which are 2048 x 768 and 2560 x 1024.
@drazkers Have you successfully used switchresx + displayport/thunderbolt->VGA? From what Matrox is saying I think the output from the adaptor plug might be too limited?
@gabonacorp I was planning to buy the DP version instead, and use it with active dp>vga adapters, but you are saying that it is not compatible with that?
The Matrox website connectivity chart says you need a 3rd party active dp>vga converter. I assume this is what they mean:
http://www.accellcables.com/products/ul ... ve-adapter
Is that what you've tried?
For this project we don't have any money for more professional solutions unfortunately, but thanks for the tip. Next time I'll try to find budget for something like that.