There are many dancing difficulties associated with the Once Removed concept:
Unfortunately, very few dancers can see who is a member of their Once Removed group when the call starts or remember who that group contained at the end of the call. They also have trouble remembering the group offset. Seeing the offset is particularly difficult for those in the very center 4 spots of a tidal formation.
The point of all this is that this concept can be very easy to do or incredibly difficult.
The existing documentation about the Once Removed concept is far from adequate to handle the many Once Removed situations that are being called today. The strategies for dancing Once Removed from Lines/Waves and Columns is different from Tidal Formations which is different from Diamonds. And the strategy may be call-dependent within any of the 4 Once Removed groups. There are strategies that are formation dependent and strategies which are call dependent. There are calls that when done from a given formation can be done using three or four different strategies.
What is a dancer to do?
It seems that a large gulf exists between what is taught about Once Removed in lessons and what the dancer encounters on the dance floor. The typical lesson about Once Removed is sandwiched in among several other calls and concepts during lessons. Written documentation about Once Removed is skimpy at best. Both lessons and documentation do not reflect the reality about Once Removed as it is used on the dance floor. And the callers and dancers don't always agree.
There have been comments on the Challenge-SD forum suggesting that the Once Removed concept be moved to the C3B list and that the Twosome concept be moved to the C2 list to help handle the Once Removed concept.
I am not in favor of either of these. Many C3A and C3B dancers have problems with Once Removed. Twosomes is a difficult concept. While Twosome-like movements may be used in some Once Removed calls (like Peel Off from two-faced lines), Twosome is a demanding concept in its own right. The Twosome-like movements found in some Once Removed situations are just that -- they are individual dancer movements that mimic Twosomes without being Twosomes.