Printed this in PETG-HF and 0.20mm strength on a P1S and it snapped right in. And whne I say snapped in, it fits like a glove. Didn't change any details for the size.
I am not sure exactly how to bend/use the tab so I left it.

I just got back from a ride and thought well that's annoying mud is obstructing the tail light... and here is the solution (saw it on advrider). (edited)