I'm doing a classic drafting problem - Belt Tightener Assembly - and the frame has a "post" that has an ellipical cross section that starts with a 12mmx32mm ellipse going to a 12mmx48mm ellipse. I lofted this 140mm without a problem. Then there is an I-beam 26mm from the bottom, that intersects the post at 90 degrees. The I-beam is 30mm tall and the width is to the tangents of the ellipical loft. The ribs are 4mm. I cannot, correctly, get the I-beam to end at the tangents, for the width of the beam. I cannot, corectly, get the I-beam to end at the surface for the length. So what is the answer?