After a quick peak we noticed the MG400 had a Core frequency of 126 MHz and a memory frequency of 168 MHz.
We took the Matrox tweak and pushed until we could go no further. At that point we went a few MHz down and voilla, the card was now running 20% faster then it was a minute ago. The final and stable result was a core freq. of 151 MHz and 202 MHz for the memory.
Considering the fact that the MG400 does not have any active cooling except a heatsink (see picture) these are pretty good stats. I'd love to mount a fan on top of it in the near future and see what results will come out of it then.