I always put my sleeve on totally by hand once the quilt is complete, so can't see a problem with adding it to an older quilt. Most of my wallhangings I do a split sleeve. The middle measurement is 15" and then leave a space for the nails, and add the outside sections. This way I can put nails in the wall at 15" apart and inter change different size wallhangings without making new holes. I think I may have read about this on Ami Simms site, but not sure exactly.