Thanks for the feedback guys. I am going to go for it and leave it outside. There is an advantage to this, and that is the root-system is now well-developed, it will be undisturbed, and growth will then probably be good next season. The plastic bag thing is one of the smartest things I've heard. I'll definately give that a shot.
I have said it before and I'll say it again; Sikkimensis knocks out basjoo in terms of growth. They were planted side by side, same size. Only 1 sikkimensis and 6 basjoos. The sikkimensis is now much taller and robust than all of them. It is also amazing that musa "helen" grown from seed this spring has grown almost as big as these basjoos! For Norway, Himalayan type bananas seem like the winners. But it remains to see who can conquer "king winter".
BTW, Since I like to brag, I promise to post a few pictures at the end of the growing season, wich sadly is coming to an end here real soon
!
Erlend