You need to expect 3 months from Entry into Service for teething problems to be ironed out. This is the same whether your talking B767, B757 B737 or A321. Only B737 with the Israeli mod are affected by the 9 G bulkhead. AEI mod is not affected. I believe there is a fix approved for the Israeli bulkhead. Not 100% sure how they are fixing it or how many man hours involved.