I have a Pro 600 and tried a double batch (12 cups of flour) and I had to take some dough out of the bowl and work the flour in slower because it was just barely too much for the bowl. I normally dump all the flour in and mix on lowest speed until combined, but the flour went everywhere. Once the flour was incorporated, I put the rest of the dough back in to blend together. The paddle did fine, even with that much dough.