Manassas event is a carry over from AACW where it was contested by both factions.
CW2 moved main CSA Army to Manassas but did not change the requirement for USA to capture Manassas or lose 10 NM.
If a CSA player just keeps the main army in Manassas, there is just about no way for a USA player to avoid the 10 NM penalty.
There has been quite a lot of discussion centered on the failure of USA players to advance until 1863. Could this be partially caused by the NM difference brought about by the Manassas event - around 81/82 USA vs 109/110 CSA in Early Oct 61.
How about modifying the event - possibilities:
1) multiple locations to be taken to avoid the penalty
2) lessen the NM loss
3) can someone come up with another possibility?