I can understand your frustration. The problem is that the 'Force Song to Simpler Arrangement' option doesn't seem to override the embellishment at all in my experience (although I'm only using v2011.5)

To do that you have to edit the current style and under the Style menu 'set embellishment for all instruments' to 0.

This should work. If it doesn't then it's usually because ninths and other extensions are part of the notation in the pattern. In this instance you could change the velocity settings to '0' under the Pattern menu targeting a specific midi note, e.g. notes 50, 62 and 74, which would have the effect of zapping any ninths once and for all.

What's needed is a more effective way of doing all this without having to go 'under the bonnet' so to speak. im coming at it from the opposite end of the spectrum where even for jazz its not always a good feature to throw in extensions. Especially as in some cases the notes don't really belong and change the harmony colour completely.

Regards

Alan