With 13 players, if there is an SK, we'd likely be looking at a 9 townie/3 mafia/1 SK split.(unless hat is as bad at balancing as I was, hehe)
Two mislynches and all townie night kills would make it 3-3-1, which is still winnable for town if the SK shoots nothing but mafia after that and mafia shoots SK one of the nights.
No lynch today and a mislynch tomorrow plus all townie night kills would make it 4-3-1, which also relies on the SK helping town to have a chance. There is a little bit more leeway in that scenario, but it's still giving up a lynch opportunity.