Hi - You should be able to make the character go any way you want by just making different shape tiles, but…
If you are trying to set the character to the rotation of the spline ( not just left and right but leaning also ), that would require a pretty major mod to the code.
When you are setting the character rotation to the spline rotation, you have the option to use ‘local space’ or ‘world space’. I’d try both, you might find one works better than the other…