That's why I tried to use Sketchup(a 3D app) but Sketchup won't play nicely with pepakura. I've been trying to do it to an already built model with no luck. So I only need to modify the width of the model in this example, in other instances like arms and legs I need them to be fatter and shorter. I know now that(using scaling like Revell-Fan) that an Ironman mark 3 helmet for him has to be 80% of the regular one for it to fit him nicely height and depth wise, but I need it to be 25% wider. Unfold it (by just pressing a button) Edit the unfolded pattern. I have already tried doing an Ironman Mark 1 helmet and I had to do a big, ugly modification so it would fit his very round head: Make 3D data (with other 3DCG software) Import the 3D data to Pepakura Designer. As tall as my son is for his age, he has a big head, short and fat limbs compared to those of an adult. Thanks cfuruti, that's exactly what I meant. Even 2D rescaling of individual parts is not generally enough: it can, e.g., make a thigh overall bigger, but not shorter or thicker. If so, this requires not a rescaling but a redesign of the original 3D model, which AFAIK is beyond the abilities of Pepakura Designer. Since the OP mentioned '3yo', it probably meant changing relative body proportions - e.g., making the head much bigger in relation to the limbs. Pepakura Designer (program-You can download from my instruction).