Bars: Cast Handstand
Casts: another one of those tricks the judges are particularly picky about, especially in the compulsory routines. But in general, if the height of your cast does not meet the minimum requirement for your level, the judges are going to take an axe to your score and chop off a nice chunk in deduction. So, how to avoid this problem? Cast as high as you can, preferably near or to handstand.
This is another one of those skills I've seen come so much more easily to shorter gymnasts than tall ones. Like many, many tricks, because a shorter gymnast's body radius is shorter, less effort is needed to rotate the body. Unfortunately, this puts taller gymnasts at a disadvantage, and it requires quite a bit more strength.
Luckily, there are a couple drills you can do, whether you are tall or short, to strengthen those muscles essential to getting a good cast.
The first -- and I don't know the name of it - is one that works on the heel drive, and the strengthening of the shoulder and tricep muscles. Lay out a folded panel mat or other elevated object. Position yourself so that your lower body is towards one end of the mat, supporting your upper body by placing your hands, with your arms straight, on the end of the mat. Using a little bit of momentum, drop your hands to the ground, kick your heels so that your body is in a slight arch, and roll off the mat into a handstand.
If this is too hard, you can stack another panel mat on top, and unfold part of it if necessary. If it's too easy, unfold it little by little until the height provides you enough of a challenge. Ideally, you'll want to be able to do it flat on the floor, but it will take some time to develop those muscles.
Another drill to strengthen the shoulder muscles is to do sets of ten hollow-body casts. These should be done all in a row, casting as high as you can while remaining in a hollow-body position. Your arms should be straight so you can learn to cast with straight arms, but I also have found that your muscles get more of a workout if they are bent as you pike back into the bar (and then straightening them as you cast). I suggest doing them both ways so you can get the best of both worlds.
If you are tall, and have a lot of trouble casting to handstand, you can try straddling into it. If you have not seen this done before, you simply cast so that you end up in a straddled handstand, and "press" (as in a press handstand) into the handstand. This shortens the radius of your body, but it requires much more strength in the arms and, in addition, the abdominals.
Don't be afraid to cast too much and go over the other side. If you find yourself going over, simply do a half twist and end up facing the direction from which you came.
Again, I stress that this is a strength skill and will take time for your muscles to develop the strength they need. Keep practicing, and in time, you should notice some improvement. Good luck!