I realize now that string tension / torsion is a big part of response on a classic wood axle. I’ve put perfectly good poly strings on that wouldn’t bind well at all, then after a few throws (and implied string rotations / extra torsion on the string) they started tightening, binding up and playing just fine. However it still does vary by string… some poly strings must not coil as tightly as others, perhaps it depends on the way they’re made?
I mentioned earlier that I accidentally put a nylon on one of the Tom Kuhn wood axles and I was surprised how well it worked.
Since nylon has that incredible tendency to coil up so tight and generate so much torsion so quickly, I’m beginning to see why nylon (or at least poly/nylon) might actually work better on wood fixed axles as @TheThrowingGnome kept telling me!