Wavedashing in PM is handled via GCT code, so I'm not sure if I can really help you there, though I would suggest fiddling with the Stopping Velocity Attribute, as I think it has to do with ground traction. Or maybe get your attributes to match Luigi's, given he has the most dramatic of wavedashes.
Edit: Yes, it's the Stopping Velocity/Ground Friction Attribute (labeled as Stopping Velocity in BB, while it's labeled as Ground Friction in PSA) that affects the distance of a Wavedash.
I've tried changing them, and while I can see the difference after they stop after a run (they slide for a bit), they still cant wavedash for some reason, they just...lose all momentum for some reason and stop