Hi Amanda. As per IBC standards, caudals which spread over 180° (over-halfmoon a.k.a OHM), is not a fault.
Halfmoon caudals are faulted if the spread falls short of 180°. At 180° or more, no fault applies. There are some judging communities which show preference towards OHMs (>180 caudals), but these are just personal preference and are not guided by any prominent standards. IBC states that "Caudal fins that exceed 180° spread are not favored over fish displaying 180° spread". So, it is clear that neither caudals with spreads above 180° nor at exactly 180° are preferred over one another.
Some things to watchout tho:
- It is important for caudals to have a top-bottom symmetry. Non-symmetry is faulted, regardless of the caudal spread. Particulary when judging OHMs in shows, this should be given particular attention.
- A common problem with some OHMs is excessive ray branching and bent rays, which are faulted.
For your caudal peduncle question, are you referring to the caudal or the peduncle? Maybe you can attach a picture which shows exactly which part of the fish you are referring to.