[Jeff Lee]

This is yet another example where it costs the racer more money to stay within the rules than to allow a piston with any ring width. The piston makers don't charge any more or less for a thin or fat ring groove. But you'll sure pay for these spacers.
No different than my argument to allow "true" solid lifters in Stock. You can buy a "true" solid lifter set for $85.00 or so, or you can spend $300-$800 on a "quasi hydraulic" lifter that only has .015" of plunger travel. In the end, the engine doesn't know the difference from one to the other. But your wallet does.