Running GMOD while on SLI mode = X

I’m running two 980Ti’s in SLI mode (when I run a single GPU it works fine) - tried googling the issue but alas, none of the recommended routes work. Does anyone have any idea of what could be wrong?
Before anyone asks, I’m not using SLI mode mainly for GMOD, I use it for other games but I don’t want to turn off SLI every time I want to play, it’s a big hassle as I have to redo all my monitor settings e.t.c.

Things I have already tried:

Setting -dxlevel’s (70-95)
Re-installing DX
Re-installing GMOD
Restricting GMOD to use only one graphics card through CP (but still crashes ??)

If you have any ideas, please don’t hold back!