Just a tip. I used to make "Jazz guitar" sounds from a clean sampled stratocaster when I was making MegaVoice Soundfonts. What I did was I rolled off a lot of the highs and high mids, and boosted some of the low mids. When I got it right it was really thick and creamy, maybe not like a fullbodied Jazz guitar, but more like an ES-335 type guitar, but with some reverb and a touch of chorus it sounded passable enough. I also removed a hint of attack, and made it linger a little bit after release. Maybe if you apply some of this to the MegaVoice clean guitar and save it as a user voice it will sound good? I assume you can do this kind of editing on the S910.

Cheers!

Doc-Z