Thnx,,,
It doesnt take long at all, and is rather easy, it doesnt take much muscle, just a constant light pressure as the heated knife edges cut and melt thru the rubber, 15 minutes for each tire to groove and another 10 minutes or so to sipe. And I did this with the tires and wheels still mounted on the vehicle.
Because the grooving was a uniform pattern all around the tire, the ballance wasnt affected and the siping removes zero material.