Sumo tips are excellent but do have the tendency to explode when you need them most. Good tip but somewhat risky. If you have one installed, be sure to have the repairman cut the tip down to at least half the size it installs at. You don't need the whole tip, you're only breaking with it in most cases. The tip will still last you a couple of years at least.
Then, tell him to give it a quarter radius. If you have a great stroke, with power and control, you can use a nickel radius.
Gene