The rear panel that the lights are on ( RLM ) is fiberglass. Is that correct. Also both sides of the rear light lens are upside down. Is that correct

The rear O/S corner panel that takes the all in one light unit on the refurbished RMLs is fibre glass, don't understand the other question.

My bus number (if any): RTL 960, RML 2667, RM 1585, RMC 1458 and 15 RTs

Not quite sure what you mean about the rear lights , but I think you'll find on most routemasters with the later lights that the orange indicaters are uppermost and the red brake / tail lights below. Hope that helps

Mark , RML2391

My bus number (if any): RML2391