Scarf Cut on windshield

My plan was to cut out the corner of the windshild and then scarf new back in. Since the windshield is constructed of two layers of 3/4" doug fir, it is a straight forward scarf. If the area is bad the layers readily separate. You can also note the screws into the end grain that are right between the layers. While I have a problem with screws into the end grain of plywood, Clyde points out that "I have only one thing that somewhat confuses me in your discussion. It is your statement that “the large screws put directly into the glue layer inherently tend to separate the two layers” but on just re-reading it I understand what you said. But, the windshield was cut to shape and the window “holes” cut out after the two layers were glued up. I made my own tests on that glue as applied to the scarph joints and found that when cured the glue joint was stronger than the plywood. Also, the pilot drills used for those screws were tapered and left a drive fit in the wood for the shaft of the screw between the threads and head. The solid tapered shaft of the screw that hold the threads applied no spreading force because the wood in that area was drilled out with the pilot drill. The threads cut a groove for themselves as the screw was driven in and the main force (if not the only force) applied by the screw was in line with the screw itself as the head pulled the house tops and sides in tight against the windshield."
The final scarfs would be 45 degrees, and offset layer to layer about 4 or 5 inches.