I can guide you for free, but you gotto buy me Tea, Kopi, Roti and pay for my game money
(Joking Oni)
To get to the ave. you desire the secrets is in the "Spares"
If you bowl a straight ball, yr chance of having splits is higher than other any styles, simply bcoz when yr ball go so straight that when it hit da pin, they all fall backwards and do not deflect or carry to either L/R.
Hence if you are serious, do consider to pick up a proper technique.
I started with Straight(Few months) to learn the basics, then Spin(Made it to 300 after 10 years) and Hook(Still learning and its quite fun).
If you have the determinated to excel, maybe I can help
Cheers