The Pattern School website I mentioned in yesterday's post is brilliant. There's so much to explore. Case in point: under the 'Measuring and Sizing' tab you'll find another version of how to make your own dress form. While I like the Etsy Labs tutorial I posted last week for the taping instructions, the Pattern School version gives a better discussion of materials and shows you how to turn the taped 'mummy' into a hard dress form.
Another page of interest is 'How to Calculate Dart Width'. There you'll find very useful math for making custom garments and for when designing around stretch factor.