Hello RedSkull,
thanks for your email and explanation in this function.
I also think overscan must be handled intelligent instead of fixed point. I tried to change the sol pointer, even in the slightest change has fatal impact to the generated VGA signal and make my TFT go crazy

Set to 454 the picture appears for 0.2 sec and disappear again. Set to 452 will show no picture at all!
I belief in time your ECS implementation will do this job as in real Agnus chip
