My only problem when using old school urethane (i.e., my Fab Blue Hammer, Fab Burgundy Hammer, Columbia Black U-dot, or dare I even say my Columbia Gold Dot) on a sport compliant/flat pattern is that it doesn't carry as well as reactive resin. It has to be flush or I'm leaving 10-pins; or even worse, an 8-10. (Essentially for me, it's been my bowling experience that translates into scores in the 170s to 180s.)