Flex Plate

Is it safe to drill the flexplate out from 3/8" to 7/16" for the converter mounting holes?
Or should I order a new one and be safe?
Chris, how much for a flex plate? It's for a 340 with an ATI converter.
Why do these places list balanced and unbalanced flexplates when the weight is supposed to be welded to the converter? :scratch:
Norm