Hi Larry,
I haven't tried percussion yet, but I see no reason why it wouldn't work.

I've I'm understanding correctly , you first want to copy a percussion part from an intro or ending and add some extra percussion note's, so that it sounds more like a fill in ?

Basically if you follow the directions in my original post, you can then edit and add/delete additional notes to your pad in steptime to fill it out a bit more.

If you've got something particular in mind, let me know and maybe I can help work it out.

best wishes
Rikki