Change from LEGACY to UEFI, Upgrading from Win7 to Win10

Hi Everyone! I am working at a company with a decent sized enterprise enviroment. We har over 9000+ computers today and most of them are Windows7. But we are in the middle of a change now, we are upgrading these computers to Win10 at the moment(including a change from LEGACY to UEFI). We are first changing the BIOS settings to the following: Boot List=UEFI Secure Boot=Enabled UEFI Networkstack=Enabled SATAconfig=AHCI LEGACY Rom=Disabled WWAN/WLAN = Enabled WakeOnLan=LanWlan When these changes are applied to the machine, we reboot it and press F12 to PXE boot it with IPv4 to apply the Win10 image. But in some cases the machine has IPv6 as first priority and IPv4 as second. Different Dell Optiplex / Latitude models show different results. This is a big problem for us because we are doing this BIOS change and PXE boot proccess remote with some machines using powershell and DellBIOSProvider tool. The powershell script works fine and changes all the BIOS settings as we want, but we can't control the bootsequence when the BIOS is swapped to UEFI. The BIOS versions can be different versions, but we have also tried with the latest version of BIOS. If anyone knows how to make sure IPv4 is always the first PXE boot option and NOT Ipv6... That would help us alot!! Thanks in advance, Linus