Valdemar Thomsen

Hello, I live in midcoastal Maine. This is not exactly the area one thinks of when bananas are the topic. I was given a 12" high dwarf Cavendish two years ago. It has been thriving and we transplanted it to a 10 gallon pot. It is now 5 feet high with 6 going on 7 leaves. Obvoiusly we take it indoors for are nordic-like winters. My question is what happens when it's too tall for a 9 foot ceiling? Can I safely lop off the top without doing harm? I would greatly appreciate suggestions from anyone's similar dilema. Thank you. . . val