I'm not a professional baker, but I have taken some classes. As far as I know, there isn't any problem with increasing or decreasing a recipe in theory. The thing to remember is that the more you scale your recipie the more rounding error will creep into the final result....especially for the smaller quantity items. For example, in a single batch recipe you might use "1/2 teaspoon" of baking powerder...but really the perfect recipe would have .4 teaspons. If you quintuple the batch and put in 2.5 teaspoons, you are now have an extra .5 teaspoons that you don't really want in there...which might or might not be a problem, but using just 2 teaspoons would be perfect. If you have a very accurate recepie measured in grams rather than teaspoons and whole egges and such you will probably have better luck making multiple batches at one go. If you want to make a really big batch, say 4x your normal, you could try finding a large quanity recipie and cutting it down by half rather than multiplying a small recipe by 4. -Al