hi i already print a 210 x 210 box in abs, without curling.
260 ° , no fan,
buildlate @ 90°
and the most important , i use 3dlac, i use it until the buildplate is flooded, it will create a sticky layer,
the box will bump from the buildplate only when it will be cold.
you will heard a big noise .
i also keep my printer in a closed small piece to avoid thermal variation.