Hi,
Sorry I forgot to put in that baking time. I bake mine at 325 for about 20 minutes, my oven runs a little hot. They do tend to brown quite a bit on the bottom so using some parchment paper to line the pan might be a good idea.
I have both guar and xanthan gum. I don't really know if they're interchangeable, I use guar for thickening hot foods, and the xanthan will thicken cold liquids. I'd try the xanthan gum in there and see how it goes.