I guess @dalto means, it is better to use only the nvidia card after all, on which I agree. I did the same on my desktop, anyway hybrid bumblebee or PRIME, are mostly laptop solutions regarding battery drainage. For a desktop, fit's only the ..bill that is a factor
I would suggest an alternate method.
Install the card on the motherboard
Boot to BIOS and disable onboard graphics card (so, Nvidia only)