10 players on the field penalty

I think the actual penalty was only having six men on the line

In college they changed the rule to no more than 4 in the backfield nstead of at least 7 on the line. They did this BC having 6 on the line and 4 in the backfield is obviously a disadvantage to th offense. In particular - for the case where the offense attempts and makes a fg with 10 men on the field BC of a missing man on the line the play stands.