 Re: labeling the shirts
It all depends on your design, really.
I've had all sorts of sizes, and seen all sorts of sizes on shirts. One thing to remember is to make them smaller (or the same size) as the label they're replacing (if a neck label). That means your relabeler doen't have to break the end stitching between the label and the hem, which makes everyone much happier (and probably costs you less money). | 
