Working over here on my NEC 1990SXi, which is 1280x1024 native.
PAL Hi-Res Laced:
There's garbage on the lower half of the screen which sometimes contains parts of the display after switching screenmode, but I'm guessing this is intentional in this preview.
Also there are appear to be scanlines on the non-laced PAL display - intentional to aid you counting lines in your debugging?
Nice to see progress - thankyou Jens!