not sure if you can grow them outside in your area(im on the othe rside of the US). you may want to shoot a pm on that subject to Tony Parobek. he grows his stuff in a greenhouse but he is in New York state somewheres and has lots and lots of experiance with Neps and should be able to answer that particular question since he is in your general vicinity and is far more familiar with your weather than i am. there are several othe Nep nuts in New England but i cant think off hand who they are. if the N. alata does good for you than i suggest N. bongso as your second step. it will be a really nice contrast to the N. alata, and its quite hardy and adaptable. N. spathulata is another good one. after that pic a nep you really want that looks like it will survive in your conditions and your set.
here is my N. bongso,