Valerie, if I wanted to do what you want to do, I would root cuttings making sure they had equal vigor, put three rooted, sprouted cuttings in one 5 gallon container and as the sprouts grew, I'd braid them, and pinch off any new sprouts coming from the soil or the trunks. What you want is 3 trunks that you can braid with NO branches. Do not pinch the growth tip. Key is, either use ONE variety, or 3 that have equal vigor.
Suzi