the lenses are nearly impossible to CAD out correctly, so if you want the fast route. take aerial image of the lens and import it into your CAD system, take a few measurements, resize the image meticulously. Proceed to trace the lens with vectors. extrude the total depth of the lens with the curvature.included (about 5mm for me). remember your doing this so you know how much space you need inside 2 tabs for a snap in.
basically my each lens is only tabbed in from the two sides, total of 4 tabs. you'll see in the pictures. for the front inner and outer side tabs, you will need want to use one millimeter wide.
for the back side you want to use 1mm for 0.5 mm for the inner tabs.
youll want to build it with the arms up, 10% fill, 2 shells, 0.4mm stepover, 110 speed (shoulda went way faster) rafters and supports. took about two hours to make this @
Techshop in Detroit. ( www.techshop.ws )