Re: What can a spotter do to better
Trace is interesting, but not that useful.
It tells you about what's happening after you no longer have control of the shot, and may tell you things that aren't true next time you shoot.
Trace can be seen from both ends of the trajectory, and could get someone shot on a two-way range.
The best thing a spotter can tell you is where your misses are going, but it's really the second set of eyes, which aren't being redirected by recoil, that makes this truly helpful.
Beyond that, a good riflescope can handle most of the rest of the things you really need to know.
Greg