See the attached pictures. I first create my 3 workplanes as shown with the different sized geometry on each one. Important, there are the same number of vertices on all 3 workplanes as Mike stated before. In the freeform menu, I then selected ""create ml"" and created the matchline (needed to guide the loft). As you can see, I select the front right corner on all workplanes. Once his was done, I lofted it and got the results in the second picture.