i take it that when i said you can't do it in that other post, it wasn't good enough to convince you? oh well...
being able to set a whole program to mono is something new that was added to the 1000 and 2500. in addition, the 2500 (maybe even the 1000 too) have mute groups, which i think are far superior than the ability to set a whole program to mono. any pads in a mute group will cut off any other pad in that same mute group.
all the 2000xl has is mute targets.
you can achieve the effect of it seeming like the program is set to mono in a few ways. one way is to set all of the pads to note-off, and make sure the duration is set appropriately in step edit so that no sounds overlap, but they end just before the next sample begins.
another way (which is what i used to do) is to have the pads in bank B mute the pads in bank A. so if you hit B1, it would mute A1. you need to set samples to the pads in bank B, but turn their volumes down in the mixer for this to work.