i think You can Force Fusion to work with Gforce in Nvidia Panels - when You set Your default Gpu and / or linking Nvidia to Fusion.exe...
i hope it works for me - have a 870M and i think it works in Fu7.5. Of course there is "No OpenCl device Found" notice, but i just ignore it - had the same issue in 6.4 - OpenCl works.
The best way (?) to check it, is to run 3D renderer in float, with texturing depth set to Float... Intel card should give You an error, while Nvidia works (?) or sth like that
