Hi Uncle Dave,
reason I suggested using user styles, is that I don't like overwriting factory data.
If you wanted to take protection off, this may work for you.
On Style Play page
Pick the style , ( make sure tab is set to volume & you can see instruments for all 8 tracks)
change the bass,
write as Current Style Settings
Whatever variation etc you choose will have your bass.
Now, when you want to play it as a full style with original instruments
Top R/H corner "Original Style Sounds" make sure there's a brown dot. When that's on, you get the original sound, when you touch it , it's off & you get your Bass sounds.

I've done it with a user style as I don't want to take protection off. Can't see why it shouldn't work if you do.