valve spring retainers

The old-school SS50 engine is back together again, and it has run, but I need to make a real testride to feel if everything is allright.
But when checking the head, I found something that didn't work.
I had made triangular valve spring retainers by grinding off parts of the originals, but this resulted in one point of the retainer getting cought on the end of the valve spring, stopping it from rotating over each other.
The solution: making a 6-pointed retainer.

from left to right:
original, old adapted retainer, new adapted retainer


Method: bolt the retainer to a piece of perforated sheet metal with round holes, then spraypaint, this will mark what you need to cut away.
My scales aren't exact enough, but you take off about 2-3 grams, this matters at 12.000RPM.