I am making my daughter a size 4 fairy tale, but I need to add about 2 inches of length to the bodice. Normally when I add length, I just add the 2 inches on the bottom. But what do I do with the darts? Do I keep them the same size/length and just move them down to the bottom? I plan to do a muslin, but I really don't know what to do with the darts!