I finally got to try Achilles' proposal, and downloaded the Intel drivers for the Iris 540, which is what is in the SP4 I have. Sadly, Intel's setup software refused to install because reasons. Seems the Iris 540 in the SP4 isn't *quite* the same as the one they have a driver for. So I'm stuck without custom resolutions, it seems. Oh well, it was worth a shot. Running the game in non-windowed mode and at a lower resolution works, even though I get black bars because the aspect ratio isn't quite correct. Thank you all for your help and suggestions! Love you all for it!