Although the verticlal exhaust I designed for my Kubota Grand L has a curved stack I still added a drainage system to the lower portion of the set up. You can see the drain hose in the photo. Good warning though :thumbsup:
Just an FYI. If you decide to put a curved pipe on your tractor if it faces forward you'll want to cap it if you tow your tractor in the rain. If you have a turbo you'll want to be real careful.