The changup has been the hardest pitch for DD (13yo) to throw consistently. I agree with an earlier post that you may have to experiment to find one that works best for your DD. We have tried the flip, horseshoe, palm/push, and double knuckle, all but the flip, DD throws too fast. One good thing that has come out of the experiment is the speed on the double knuckle is about right in the middle of the speed of her fastball and flip changeup, which makes for a good offspeed pitch. When DD commits to the flip (backhanded change), and by commit I mean throws it with the same intensity as her fast ball it is a really good pitch. Our problem is she tends to slow everything down for the flip change and it either hits the ground or sails high. It is a work in progress.