For those trying to follow along at home, see my response at
http://ecomodder.com/forum/showthrea...tml#post538300
There are an infinite number of
superellipses between the circle and the square. One should closely approximate your cab's lateral profile.
The Template coincidentally matches your circular arc, but not the design in Permalink #2.
For the longitudinal profile instead of your circular arc, follow Mair:
Subject to your approval, of course.