You might also suggest to Yamaha, the next time they survey you, that the Preset Styles be made editable, or replaceable (with the same name) like many other arrangers (Korg, Roland E/G for example) allow. It seems pointless to do a minor edit (or even a major one) and have to store that as a User Style, while the useless ROM style remains inviolate.
As convoluted and with as little available memory as Yamaha make getting to User styles, using up what little you have just to store minor edits of the ROM styles (which actually aren't ROM, but simply a different set of RAM area) is a bit of a kluge.
Editable Preset Styles... Every arranger should have them!