S300 is just an awful shaft. It’s too heavy overall and too stout in the butt and mid section but with a comparatively softer tip. This results in a awful boardy feeling, it’s really a disaster of a profile. Who does it fit, really? I bet close to no one and yet you find it everywhere.
I would suggest that the OP change to x100 immediately, not because it will positively contribute to his game but because it will make golf much more enjoyable.