There are many pattern systems out there, and many ways you can measure the human form. I just need a compatible set. The Joseph-Armstrong textbook Patternmaking for Fashion Design is pretty much an industry standard in technique, but provides no reference charts for working with standard sizes - only how to take your own custom measurements and apply them to the drafting tutorials. The ASTM chart D-5585 seems comprehensive, but is actually missing many of the specific measurements necessary for the Joseph-Armstrong method.
I think I've finally come upon a working solution, and am moving forward. I am happy with my first draft, though it still needs some tweaking. The first pattern I plan to work on for Rocky Horror is Janet's pink dress. It's a pretty straight-forward design.
So as you can see, this is just a basic bodice sloper, but it's the foundation I'll be working from.