ive got a 6x 750ti rig running right now using this. gigabyte windforce gpus on a z87-g45 mobo... trying to get a 7th gpu to recognize.
I too, have (a couple) of z87-g65 motherboards filled up with Windforce 750 Ti's, trying to squeeze a 7th card in doesn't even post. The screen looks and behaves like a NES cartridge with dust before the bios can even load. Let me know if you make any progress.