rimBack property
Rim strength on the side facing away from the light, relative to the lit side (0.35 = the pre-17d literal, shipped unfitted). Task 9 measured a fixed light with a directional mismatch — the device rim is brightest around 135°, where the model's 315° light is weakest — so this key exists for a bounded refit; it is not itself the measured far/near ratio.
Implementation
final double rimBack;