75mm lens holder

Holder for 75mm aspheric plano-convex condenser lens, "75mm-LED-convex-lens-Glass-condenser" ebay item 131781069708. These are I assume made for car headlights; it works OK as a LED collimator. The OD of the lens is 75 mm but there is a flat rim so the optically useful diameter is about 70 mm. Focal length is 50 mm, so the lens is f/0.7 (approx). The first photo shows it next to a similar holder http://www.thingiverse.com/thing:318346 for a 50mm condenser lens.
If you print two of these, you