If you have software, you can change some of the appliques you have to a lighter stitch raw edge. The leather needs to be fairly thin. Maybe in some of Anita Goodesign's older fashion sets and they had a clear explanation of how to proceed with leather. You could probably just contact them by phone and ask for suggested sets for leather.
Thank you,I will try and e'mail them see what comes back, I have worked with leather before. have a lot of small pieces