OSX Won't Boot With Graphics Card

Hi,

Specs:
GA-Z97X-UD7-TH
Samsung 840 EVO250 GB SSD
32 GB G Skill DDR3 RAM
Intel i7 4ghz CPU
EVGA GeForce GTX 970

I just successfully installed El Capitan on my build, and everything boots off built-in graphics. When I try to boot with my graphics card, I get an error (picture attached). I've installed the NVIDA drivers, and tried some boot flags. Any ideas?

Try booting with -f.

-f seams to work. Is there a permanent change I should make to boot properly?

UPDATE: -f only worked once, upon restart same error as before when booting with -f