Bill I had that wrong in my first post. I wrote that I flipped it upside down. That was my original intent and it would have put the back up lens in the correct spot with no modification. Since the lenses have a top and a bottom and curve upward that wouldn't work. I instead shifted the the R lens to the L side. That is why I needed to cut it out for a new back up lensHey Randy, I don't even have a stock tail light to look at, but I'm remembering a slight angle to the lens. If you look at one isn't there a difference in the amount of red plastic from top to bottom?
I corrected the posts to remove the wording that I flipped it. The lens has the same amount of plastic side to side but not top vs bottom. Sorry for any confusion