According to the ASUS Rampage V edition 10 Manual Page 1-8 cards in slots on a 40 lane CPU which mine is.
PCIEX16/8_1, PCIEX16/8_3 and PCIEX8_4 should be able to be configured as x16,x8,x8 however if you try to do this you will end up with x8,x8,x8 regardless of the fact that
PCIEX16/8_1 is loaded with a PCIe Gen 3 x 16 video card.

PCIEX16/8_3 is loaded with a PCIe Gen 2 x 8 Raid or 10Gb SFP

PCIEX8_4 is loaded with a PCIe Gen 2 x 8 Raid or 10Gb SFP

This forces my video card down to x8 which is unacceptable, I tried putting in a bug report on ASUS support site but it always does the same thing constantly:
"the site is busy please try again later".

I have tried forcing PCIEX16/8_3 and PCIEX8_4 down to GEN2 and even to GEN1 and it makes no difference, I have swapped the video card for an identical 1080Ti in my AMD system and that makes no difference ( the 1080Ti that reports x8 on the Extreme 10 reports x8 on the AMD )
The only thing that does make a difference is removing either the Raid Controller or the Ethernet controller.

O.K Have determined that ASUS needs to give us closer to bare metal control in the BIOS for PCIe lane allocation... Here's what I did.
As above my system reports x8,x8,x8,x8 If I have my raid controller and my 10G SFP installed.

Checked the card edge on the video card was cleaned and used an ESD safe blower to clean the first PCIe x 16 Slot, no change card reports x8.

In Bios changed the setting.
Advanced->Four way configuration from Auto to x16,x8,x8,x8 - video card now is showing as x16 under Tools->GPU Post. ; However the M.2 Driver disappears - found in manual page 1.6 : 40 Lane CPU in 4 way configuration PCIEX16/8_1 is used in x16 mode both m.2 and u.2 drives will be disabled.. GRRRR.
Used the dip switch 4.2 From page 1-13 Illustration 9 to disable the 2nd PCIe Slot which I can't use because it's under the video card heat sink which should free up 8 PCIe lanes. Nope still no M.2, went through all possible settings in respect of 4 Way and Auto mode with USB3 enabled and disabled - no M2.

Can someone at ASUS please give us bare metal access to these PCIe controls, I have been inforrned by BIOS moders that the code to do this is in the BIOS but we don't have access to it. We brought expensive motherboards so that we could control things the way WE wanted not to be pipped at the post because ASUS thinks we are idiots who can't work things like the number of free PCIe Lanes for a particular CPU by ourselves, otherwise we would all be buying AIO desktops and having our hands held.

I want to be able to have x16,disabled,x8,x8 four way configuration with the M.2 please.