They’ve been the standard balls for so long I guess I never noticed. Look up the PBA oil patterns. Here they are: https://bestofbowling.com/bowling-oil-patterns/
A standard oil pattern will actually help rec players and funnel the ball to the head pin. But the pro’s have moved to oil patterns that are the opposite.
The two handed bowlers are something else too! Belmonte (world champ) doesn’t use a thumb hole but can out rev any 1 handed bowler. Some say it’s not fair, but it’s within the rules. It’s fun to bowl 2 handed to watch the ball reaction, even with house balls.
Just drilling a ball is beyond me. They have programs to do it in the pro shops.
A great documentary to watch is ‘A League of Ordinary Gentlemen’. Bowling was the top sport in the 50’s iirc and then dropped out. Hired a ‘hype’ man and he brought it back with TV’s help. Interesting for sure. It’s free on VUDU (with adds) and youtube.
https://www.vudu.com/content/movies/details/A-League-of-Ordinary-Gentlemen/59779
