It’s pretty much impossible to become an excellent hand balancer if don’t have very strong abs. Without strong abs your back has to over compensate and you don’t want that.
Here are five exercises by Incite Fitness on parallel bars which will help strengthen your abs:
1. Leg Raises
4. Knee tucks
Some of these are pretty advanced, so you might want to start with something a bit easier. Check out my Ultimate Guide to Bodyweight Ab Exercises to discover the best bodyweight exercises for abs development with tons of progression workouts.