Michael - Having a specialized Toroidal Helix command sounds llike a bit of a temporary solution. As you mentioned, it's not practical to make a helical version of every curve type. So why not have an "Around Curve" option as in Rhino?

Brian - There is a very easy way to control the "tangent spin" on the swept surface. You need to run the sweep using 2 rails. Just make two helices with same # of turns and same starting point, but give them different radius values.

jonah