The No Rival does not use the same core as the Arch Rival unless a few websites have the differential numbers messed up for the Arch Rival.
In 15# the Rival and No Rival have the same core with 0.046 diff.
The Arch Rival has 0.056 diff. at 15#, so it should flare about an inch more for most people.
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"A word to the wise ain't necessary -- it's the stupid ones that need the advice." Bill Cosby
"Never argue with an idiot. They bring you down to their level and beat you with experience."