The only thing I could think of is reading something about it needing to be 19% modified from the original version. What that means exactly, I'm not sure, but remember picking that up reading about reselling modified baits/lures.
Some craws I made from my first plaster forms. Sealed forms with Elmer's Glue All. Worked great with melted down old baits. Can't wait to try with real plastisol!!