i tried gc a fiberglass pool project where I would buy the pool direct from the manufacturer who would install with no concrete, and then Inwould find contractors for the other pieces. In talking to a bunch of local landscapers (who do good work), most of them had no idea what a locking collar was for a fiberglass pool. They said they follow the manufacturers instructions, but I didn’t have confidence in things getting done right. I would make sure the locking collar is done by someone who knows what they are doing, and from what I understand Stone/paver/porcelain coping is attached to the concrete collar using adhesives. I am not sure how it works if your are using a concrete coping.