I am looking to buy this board and have a question about PCIe lane allocation.

Using a Core i7-6850K (40 lanes) can I do this:
PCIe 3.0 Slot 1 - GPU @ 16x
PCIe 3.0 Slot 3 - GPU @ 16x
U.2 - Intel 750

looking at the ROG Forums it appears that the M.2 slot turns on whenever the U.2 slot is on. Will I still get X16 for the video cards or will they drop to x8?