I tested already 1280x800 resolution and works properly with my previous calculations.
{HDMI1280x800_60, 0,83460000, 0, 1280, 800, 1680, 200, 64, 136, 828, 24, 1, 3, 1, 1, 0, 0, 0},
{{Video ID , 4 , 0, 96, 5, 3, 3, 1, 1, 0, 0, 0, 144, 64, 136, 32, 28, 1, 1 }},
PLL_VIDEO 334
In addition, I did the calculation in a different location and width of sync pulses (another school ) - it also works properly.
{HDMI1280x800_60, 0,83910000, 0, 1280, 800, 1656, 32, 32, 312, 841, 17, 16, 8, 1, 1, 0, 0, 0},
{{Video ID , 4 , 0, 96, 5, 8, 3, 1, 16, 0, 1, 0, 120, 64, 56, 32, 41, 1, 1 }},
PLL_VIDEO 336
Personally, I am use this second setting.
Can you add it to Armbian?