I think wheat protein isolate might make it gummy. If I remember correctly, it's very high in gluten, which is what gives flour its stringy/thickening properties. If you want to use up wheat protein isolate, you should be able to substitute it for any recipe calling for gluten flour (aka vital wheat gluten). Gluten flour is 80% protein. I've never seen wheat protein isolate, but I use a fair bit of gluten flour. Deb, since you're in Tee-Oh, you can get it at Bulk Barn. Come to think of it, Bulk Barn is a must-visit when stocking your LC kitchen: you can get gluten flour, soy flour, bran, ground almonds aka almond 'flour', cocoa, unsweetened chocolate, spices, flax seeds, nuts, nut butters...

PS - I edited the original post so no one jots it down without scrolling down to see the correction. Thanks again for the recipe, Diane - I'm going to try it as soon as I make room for it in my freezer. Congratulations not only on losing weight, but establishing a healthy home-cooking habit. Ain't cooking fun?