Hi TimothyO -
Yup. I've done the same experiment twice now, one with a matched set of PDs about a year ago, then again about 2 months ago with two P1s. I have come to the very same conclusion. It's not even close, Gut/Poly wins the spin contest by a wide margin.
(9x) Donnay Pro One 16x19 | RPNY Leather | 12.6oz, -12Points, ~335sw | M:16g Wilson Nat Gut, X:16g MonoGut Zx Red, 60/58 | Benchmarked USTA 4.5