IF you have to tighten the center stone I would vector tighten it. I
would suspect this was done in platinum so I would see where the
stones are being set and then set in which order I felt best.
Probably center first for support but if not you could devise a
support system for the prongs while you set the stones in them. Then
you would still vector set the center. I will assume you know what
vector setting is If not let me know.
The Jewelry CAD Institute