I am having second thoughts about the screw in cap. It looks like it will work well on a lens where the filter thread goes right to the edge of the lens (as in most lenses). With this lens, however, the filter threads are inset from the edge of the lens and there is a substantial area of perfectly flat metal lens barrel on front before the end. I think it would be too hard to unscrew the very flat metal cap when the edge is so far inset like that. The metal is not thick enough to get a good grasp.
I may just look for a thinner (non pinch type) plastic cap.