You mentioned having "a frontlit mod that is very similar in quality to the original GBASP (as it uses the same orientation of frontlight, and the same light itself) and it's pretty fantastic."
Is this the same as the kit linked above that isn't great?
I obtained a modded GBC and I'm pretty disappointed by the curved vertical lines above the LCD itself. Colorless banding, effect of a polarization filter? They appear and shift as you tilt the GBC and I'm reading this is normal of all AGS-001 frontlit screens. I keep losing focus on the game and my eyes refocus on the lines above it. Distracting.
Edit: tilting the left side of the GBC minimizes the odd properties. So these screens turned on their side for this mod explains the vertical lines? When they were meant to be less visible horizontal lines on an SP screen that was always angled away from your face?