I did a similar cruise NY - Quebec and Quebec to NY. I did the b2b = 2 cruises, same ship, but I did have to change cabins. I booked 7 days prior to sailing. NCL chose my cabin. NCL waived the solo supplement fee. It cost me B4 taxes, gratuities, and port fees = $399 EA CRUISE!!!! I was on the ship for 20 days on 2 cruises for $800!!!