Help me develop submarine pitching style!

I am an 11 year pitcher I throw a curve, fastball, and a submarine pitch. I am one of the fastest pitchers in my league and I still have a year left in little league. I am fairly tall for my age (5’ 4/5) and I am not skinny but not fat. My submarine isn’t THAT accurate but when its a strike they miss or just watch because it’s 10-20 miles slower and it has a different spin. What my question is how can I get it to be more accurate?

My tip: Ditch the submarine pitch, you’re 11, learn how to really pitch. The only reason kids at that age kids cant hit it when its a strike is because 75% of them cant hit a fastball down the middle regardless of slot.