Could anybody tell me about PT dimensions in comparison with Scout backup light?
Nearly identical. The PT is a hair thicker.
How exact do you need? I'm sure there are some photos floating around the net I could dig up.
The PT is definitely the superior light, though. Double o-rings, no danger of flooding from turning off and on, and threaded for the entire way open and closed, so pressure will not turn the light on (unlike the Halcyon).
Edit: Found SparticleBane's photo. Scout on the left, PTs to the right: