UPDATE: After some experimenting, it seems the flickering black borders are directly related to frame rate, and the G2s narrow viewport/gasket was just hiding it until now. If I lower settings to get around 60FPS, the effect dissappears.
So I guess there’s nothing to do except use the standard G2 gasket until they invent more powerful hardware or, hopefully, optimize better!
If anyone has had success with a G2 wide FOV mod, please let me know!