All oil-based plastisols are basicly the same and can be mixed in any combination, to any degree. Read the "Plastisol 101" thread...we're dealing with a 3-component chemical, and other brands are comprised of the same thing. There are different Brands, grades, qualities and characteristics, but they're all oil-based plastisol.
Mix them how You see fit. That's how I roll and I enjoy the results. PVC, Plasticizer (softener), and Stabilizer...those are the 3 components...more plasticizer/softener softens...more PVC hardens.