it is possible to add text blocks. you might be able to add a "+" in the appropriate place. i'm not sure how scaling would affect it, but playing a few minutes in pep designer would tell you.
Thanks for the suggestion. Text can be used, but any scaling or inversion can disorient the points. I am just adding a custom registration design in my 3d models that pepakura will print as cuts, but are easy to recognize as registration points. Thanks again though!