Been there and done that. Was a total waste of time and money. Unless you're hogging these out for a prostock application there is sufficient material in all the right places for a mild porting job. If you plan to port to the max, cutting one head to see thin spots doesn't mean the head you port will be better or worse. You'd be far further ahead to buy a set of the Direct Connection porting templates and use those. Those pretty much guaranty you won't grind into a water jacket and the end results actually provide a performance gain.