Hi lettuce,
So does this happen all the time or only if you enable the -powerstrip option?
By now, we can't really tweak geometry settings when working with the powerstrip option, as these are the only values actually considered:
26000.00-68000.00,48.00-60.00,0.636,3.813,1.906,0.318,0.064,1.048,0,0,1080,1080
(the other ones are ignored)
This is because, with the -ps option, modeline values are not really calculated but just read from the hardware ports by means of PS, using the default desktop resolution. We then tweak the timings to adjust the vertical refresh, but that has the side effect of modifying the porch values to some extent, so that's probably what you're seeing. However, in the monitors I've tested this has no visible effects.
Hopefully when the PS integration is fully implemented we'll recalculate the whole modeline to avoid this issue.