twill be nice ta do yer testin, but there are more facters than jest havin sumpin round and hard inside da patch. Pure lead or as near to it as possible is best. Ifn backstop lead is mixed, one pot twil be differn from the next. The weave of the patch needs to grip the ball, actually impress on it in order to get accuracy. Otherwise the ball will not spin with the patch and there is no accuracy. Best of luck.