Looks great! I love stamp projects. I’ve tried a few myself. 
I finally tried polymer on the recommendation of a post by @cynd11. There is really good advice on stamp making in this thread.Art Laser Polymer Stamps How To
It led me to try polymer. It’s fantastic on the the Misti. Does the low-odor rubber material work wll for you on the Misti? Since I have some rubber stamps, I’ll try your method on the Misti. Thanks for sharing!