I tried adding a bunch of chili powder and cumin to the bottom layer, but the batch was so large, it barely made a dent.
The recipe says it'll fit in a 9x13 dish, which is the size on the right. And I think both of these are really too full, so I'd say make a half batch. I don't dislike it enough to throw it away, but I don't see myself making it again. I add a ton of hot sauce when I eat it, and it's fine, but I'll be glad when I've finished it.