I can’t find an exact number per ballpark. But Braves Field (of the Boston Braves back in 1915) was the largest baseball field of all times, field-wise that is. It was 400ft to the corners and about 500 to center field. you can imagine how far a ball could roll in that stadium. It’s just a guess, based on the number of times that a field is mentioned in relation to in the park home runs. Also this was from further back in the early years of baseball when the ball didn’t bounce around as much. so it would be more likely to dud, and not play off a wall like modern ball. just a guess. i’ll see if i can find out more, if i do, then i’ll repost.