Thank you, that is super helpful! Unfortunately I think it is too small to fit the light I was thinking of. I'll keep looking for another way to sneak a light in.
Thanks for the install video, I have a favor to ask regarding the diffuser. Are you able to measure the center triangle of the diffuser? I want to see if one of these would fit in the center to improve the reverse lights. I think the larger one (2.5" x 4.5") would be too big.