it’s just a suggestion, but try making Vs to fit each point,
leaving the “legs” a little longer than you need. If the star is unevenly
cut, it may even pay to number the points with a fine marker pen and
scratch matching numbers on the inside of the Vs.
Once you’ve made your six carefully matched Vs, patiently fit them to each
other using the star as a template. Try doing this on a piece of
plasticine into which you can press the star so that you can easily test
the accuracy of the fit against the girdle of the stone.
When this is complete, press the fitted Vs lightly into the plasticine and
remove the star. Mix up enough investment plaster to cover the setting
components. Let it harden. When you remove it, the components should be
held in place and ready to solder. Clean off any waxy residue with a soft
brush dipped in methylated spirits. When soldering use a soft fluffy
reducing flame so that the plaster is heated evenly with the metal and
solder it all together.
I know this might sound like a lot of work, but you will end up with a
beautifully crisp, neat and accurate piece of work which will do your
reputation as a skillful craftsman no harm at all - not to mention the
satisfaction of a piece well made.
Kind regards, Rex from Oz