I had this done once, and it did work well in order to extend the lifetime of the engine. The pinched set probably did not last as long as a new set. I'm not a top-level driver, but I found the performance to be good -- I did not notice a loss of power compared to when it was still new. If you're trying to win the nationals, your may have a different opinion.

Hence, for most racers, a great way to extend the lifetime of your engine without breaking the bank.