Whilst testing the Mode Extension Module in Grievous Bodily 'ARM, I noticed that the translation of type 0/1 to type 3 doesn't appear to have the desired effect on IOMD. It works just fine on the Pi, on IOMD however, RISCOS is resetting the screen geometry to the base MODE.
At a guess the issue is due to RISCOS' reliance on bespoke resolutions being defined in the current monitor file, I need to investigate and find a fix, as Mode Extension Modules only work if the game subsequently reapplies the VIDC parameters, this can be seen during the loader in GBA where the screen is scrambled on IOMD.