thank you ShintaiDK, i also called owc tech support and made sure,i was almost ready to get a crosshairV board it has a x4 pcie slot......You can plug it into the x16 slot. You can also plug x16 cards into open x1, x4 or x8 slots.
And you wont lose performance by plugging a x4 card into an x8/x16 slot.