You still need to set the GS to output the VMode you want, for example VESA-VGA-Modes...
There is an open-source-application developed right here on PSX-Scene (by doctorxyz and dlanor), which is called 'GSModeselector' and is intended to be used for this case(s).
PS2 V7/DMS3 V2 (FW:2.4b7); Seagate Baracuda 200GB
PS2 V7/CC1.0 (FW:34 hacked v2 BM:2.1.6); Maxtor DiamondMAX9 PLUS 160GB
PS2 SCPH-30004R; NoMod+NoLaser
3xSony MC 8MB
MAX/Datel 16MB with Boot-CD
Custom FMCB 1.8b+ Beta-Build, my AIO 0.5, Sony&xRhino-Linux