Dntm, I won't say that it is not money well spent but it probably isn't necessary. I run the same spinner you do & a Biela CF prop. I did the knurling of the center myself with a heavy wire wheel I after 7 gallons of fuel mine hasn't slipped a bit. I do torque the devil out of it any time I remove it though. There are a number of people who removed the 2 small guide bolts & replaced them with longer ones which go all the way through the backplate & prop. I think this is a false sense of security as one good backfire would snap them right off because they are so small. Mine needless to say has never backfired. I guess I am torqueing my prop nut down at right at 40 lbs of force and it has never slipped. Don't be afraid of that engine but do treat it with respect & it won't give you any trouble.