Side STF
It isn't obvious, but I made a mistake while drilling the holes. Because of the way I transferred the bolt pattern between the mounts, the screw pattern on the new mount was the mirror image of the original. Since there were four evenly spaced screws, the mirror image was the same as the original. Unfortunately, the orientation of the 4 screws relative to the top of the lens was not symmetric. While I carefully matched the top of the lens with the top of the Canon body, I forget to reverse the offset to account for the mirroring. Now, the lens is about 15 degrees off center. It took so much hand effort to get the mount to fit that I did not bother making another one to correct this problem. The lens and hood are otherwise rotationally symmetric, so this slight rotation did not matter.
Sunnyvale, CA
Side STF
It isn't obvious, but I made a mistake while drilling the holes. Because of the way I transferred the bolt pattern between the mounts, the screw pattern on the new mount was the mirror image of the original. Since there were four evenly spaced screws, the mirror image was the same as the original. Unfortunately, the orientation of the 4 screws relative to the top of the lens was not symmetric. While I carefully matched the top of the lens with the top of the Canon body, I forget to reverse the offset to account for the mirroring. Now, the lens is about 15 degrees off center. It took so much hand effort to get the mount to fit that I did not bother making another one to correct this problem. The lens and hood are otherwise rotationally symmetric, so this slight rotation did not matter.
Sunnyvale, CA