Hey Don, sorry I didn't see this sooner. I have some experience with snake skins. I have been doing taxidermy for way more years than I want to remember and have prepared snake skins for display, mounts, and craft use. I have the best results with tanned skins. Ones that I stretch and air dry without any preservative will have a greater amount of shrinkage during and after the drying process and can warp and wrinkle even after drying. Skins that have been properly preserved/tanned normally don't have this problem. I have 2 prairie rattlesnake skins for a customer tacked out for air drying right now. He will cut pieces and glue them onto the barrels of custom made ink pins and will put a clear coating over them. He doesn't want them tanned because some of the chemicals used in the tanning process might not be compatible with the clear coat that he uses on them. I can tell when they are dry by watching to see when the skin shrinks to the point that the edge of the skin tears from the pins that are holding it to the stretching board. The air dried skins are paper thin and will crinkle and wrinkle like paper and can break and tear. Skins that I tan have almost no shrinkage and are flexible and even stretchy when dry. I would recommend tanning the skins that you have because they will have a longer life span than skins that are air dried. I haven't used any of the home made tans like you reference because I want and expect consistent good results. One of the easy to use tans that I use is called "Snake Tan" and is available through some of the taxidermy supply companies.
You can PM me if you have any questions.
Royce