To answer your question yes you can over fill a lower. The lower needs a small void area for heat expansion. Early 3L Mercs have been known to only put 32oz in the lower or the oil can push the top seal out. I have found some motors that you can not let all down for correct fill check and I will refer to motor spec`s for lower units capacity.
“The world will not be destroyed by those who do evil, but by those who watch them without doing anything” GOD IS GOOD