Of course substituting gluten-free for regular flour would make all the difference. You will be happy to hear that in my upcoming cookbook, I make ample allowances for gluten-free dishes, both savory and sweet. Until my recipes are articulate enough to share (the book is due in June 2011) let me already say this to you: 1. Don’t use all tapioca. Rather, use a mixture of brown rice flour, tapioca and other flours you will experiment with until you arrive at the texture you like. 2. Add 1 teaspoon xanthan gum. 3. don’t pour the batter in one large mold, but in smaller molds, such as muffin molds.
In the absence of gluten, you need to make some concessions, and once you learn to work with them in mind you will be totally OK!