First lens almost done.
Final fitting and drilling holes, next.
I dry-fitted the lens into the bumper opening using short sections of the silicone hose draped over the edges. If you were right in your measurements, the lens should fit snugly in the opening and flush (well..., almost flush) with the front of the bumper. Get some silicone hose (3mm ID) in color of your body, cut it lengthwise and drape it over the edge. This is your weather-seal.
Depending on the hose wall thickness, small adjustments to the lens perimeter are required. To achieve perfectly straight lines I used rough surface of my concrete driveway (equivalent of 100 grit paper).
Projecting the screw holes onto the lens is tedious and PITA, but I make it easy for you. They are 43mm up, measured from the bottom of your original perimeter line
(not the "adjusted" inboard line!). The inboard hole is located 22mm from the "original" (!) vertical line/wall, BUT outboard hole is only 20mm. (Remember? The "adjusted" line should be inboard of the "original" perimeter line and the distance=wall thickness of your hose/weatherstrip).
Word about screws: You'll need longer screws; use stainless sheet metal screws, 1-1/2" long (you may need to shorten them to 35-38mm), size #6, Phillips or truss head (as small as possible);
FYI: best assortment of stainless fasteners you can find here: Hex Nut - Carriage Bolt - Brass Fasteners - Fastener Supply - Threaded Inserts | Albany County Fasteners
Pay attention to the lens fit in the corners - if not exact, they may not seal properly and allow water ingress.