Thanks so much for this-- worked for me.
I just updated my system from El Capitan to High Sierra 10.13.2 via Unibeast + USB. It was a bit of a tricky process because I had to wrangle with an R9 290 (non-X), custom card (Gigabyte Windforce OC) plugged into a 4K monitor via DisplayPort. But in the end it worked out (with Lilu, Whatevergreen, AppleALC latest kexts in EFI in Other + Clover 3297 installed as legacy + DSDT), and I can boot into High Sierra finally!!! I haven't had a chance to test/bench yet, I was NEVER able to get Sierra to work on this system with this GPU, and even on El Cap I was unable to change anything in the Displays preference pane (like scaling or refresh rate 30 vs 60)-- but all that seems to be working now.
Next step is to test FCPX, Lightroom w/ GPU acceleration, and a few other required things.
Very exciting how this has given new life to this old system. I hope I can hold out for mainstream 8 cores or HEDT higher core counts now!