Don't worry about it. Just remember with big beers you need to set up a blow off tube for increased pressure and high krausen. I've never had high krausen blowing out my tube but many others have. Colder temps will help, my Imperial Stout I just made just before the new year was fermenting around 50 degrees in my apt, but the fermentation brought it up to 62-64 degrees I think. It heats up big time.
13+ gallons sounds like its going to be a great fall and winter! Thats a lot of RIS!