The 2nd time, I doubled the recipe, but I didn't double the recommended size of the dish. I squeezed it all into a pan that was smaller and, although it fit, it wasn't as good. The crumble topping really does need to spread out over that area. Also, don't cut down the amount of butter (or, in my case, margarine). I thought it called for a lot of butter/margarine when I made it the first time (only because the quantity seemed like a lot, not because it tasted like too much), so I cut some out the 2nd time, and it wasn't as good. Use the full amount!
Follow this advice, and you'll have a delicious autumn dessert (or breakfast! Why not?!).