Ahah... but there is a problem, David.
Your script creates a pointlist with ALL the arc centers in it. Thus, one arc and its accompanying center cannot be moved as an entity...all the points must move.
My script, simple as it is, creates a separate pointslist for each arc, so they may be moved around at will.
As I look at this more, the routine should also draw a ray from the arc center to the arc (which can be deleted if not needed) so that it's apparent exactly which point(list) should be associated with a particular arc.
(At this point, it's a pity there's no way to "group" objects, so when one is selected, all are.... Andy?)
I shall work on that, too! (Please, you do also... your code is much better than mine!)
LLoyd