In my never ending quest to get GOP boot screens working on the 4,1/5,1, I've had an odd day. I won't go into all of it, however I have something new for 4,1/5,1 users to try. Clover in UEFI mode, installed to an HFS+ partition of a Master Boot Record disk. First thing you need to do is make an MBR disk and add one HFS+ partition, can be USB or a SATA disk. Next copy this folder to the root of the disk: https://drive.google.com/open?id=1O-NadML8iKycC4UQsDZguXUS01fv-jiV Install a GOP card with a Mac EFI card and reboot, holding Option. You should see a disk that is EFI Boot, boot from that disk and see if Clover doesn't load on you GOP video card. Let us know how it goes.