Which reminds me:

You could also use the 2-voice pitch shifter among the insert EFX (no. 22) to fatten up a patch. I've never tried it because I've just gotten so wedded to doubling/shadowing parts, but I really ought to and keep telling myself I will, since it would save memory in the song (not having to double the part).

This EFX seems to be implemented in a pretty streamlined, simple fashion essentially as a detuning device. It's worth a try.