are you tiniting the whole thing. cause if you are i would just take it out...if not. take and put tape on lightly cut it out dont press to hard maybe?
Here's a beter way. Lay some masking tape on a clean table. Guess you would need like two or three strips of it, lay them next to each other so it's approxamite the size of the reverse light. Now, get a protractor and measure from the middle to the edge of the reverse light. I hope u know how to use one. Then draw the circle on the layed tape and cut it with scissors, peel off from table and place on light. Violà
protractor ftw!!! lol