Agrelon congrats with your school and location choice! It's a great town...
On your Q, given that I am windsurfing and SUPing in Denmark, I am typically using a 5/6 mm for winter and 4/3 for summer. Now, the best suit for COLD conditions that I plan to buy to replace my old Winter wetsuit is an
ION FUSION Neopren Drysuit! This is a full dry suit, designed to work with a set of thermals underneath! I have a friend that bought last yeats model and he said that, the suit kept him dry and warm in zero conditions. The Fuse is actually combines all the best traits of a baggy drysuit and a neoprene wetsuit without any of the weaknesses. Check it out at
IONs Fusion Site. Buy some good shoes and Dakine mittens and you are SAFE rather than cold....