I used both some calculations and the TAR method to come up with a reasonable shape for the nacelle.

I used the center of circular firewall as a reference for calculating the radius of the formers. On the plans they give you the side profile of the nacelle. A horizontal line thru the center of the firewall gives you the reference line. Decide how many formers do you want along this line. At every former location draw a perpendicular line from the reference line to the outline of the nacelle. The length of this perpendicular line is the radius for the specific former. Use this to draw a circle. Cut that in half and then shape the halves to fit the two sides. As you move back along the nacelle outline the formers will get smaller and each would have to be shaped for their specific locations.

Hope this makes a little sense.