I am almost finished building my dome observatory, but I am having a little problem with rotating the dome (which is why one choses a dome in the first place ). I am currently using a steel rail with steel V-groove casters (photo attached). The problem with this is that there is a tendency to derail the casters from the ring. I wonder if rollers would be more forgiving. Robert Hayes' rollers/ball casters look interesting. Appreciate your help.