Vertical : 50 - 76 Hz
That could be why it doesn't hold DblPAL - that mode is slightly less than 50Hz.
Can you live with DblNTSC - use Overscan to increase the screen size and you don't lose too many lines, it runs at 58Hz iirc. Will VGA/MultiScan work? I think it's supposed to be designed for "normal" PC monitors...