Some games just don't work in certain forced video modes. I've tried a few games from HDL forced to 480p and 720p for my component cables on my CRT 720P set, none have worked so far. Of course, I only used GSM to keep snes station from flickering, which it works to do. I'm trying games here and there on different video modes.
SCPH-39001 V7 GH-019, fliptop case, FMCB 1.8, 80GB HDD (SMS console) 16MB card running it all
SCPH-39001 V7 GH-022 FMCB 1.8, 120GB HDD (Game console) 64MB card running it all