I had posted this before and was looking for it (to remind myself how I did it) and then saw the "slimmed down" note, bummer.
I remembered so thought I'd document again. If you want to convert your 4/4 styles to 6/8 shuffle do the following:
1. Select your style
2. Go to Style Creator
3. Go to Groove Tab
4. Under "Original Beat" choose 16Beat.
5. Under "Beat Converter" choose 12Beat
6. Pick a variation (A,B,C, or D) under Style Control (where you normally change variations while playing)
7. In the PopUp that says "Section) scroll up to "All" and click Ok
8. Select Execute and then save your file (to a new name)
Thx,
NASAMike