Quoted from pindude80:I'm thinking the reasoning behind the mini-flippers and mini-balls is because they wanted to put as much as possible down there, which they did, and there wasn't room for full size bats or balls. I think they made the right decision because the AC/DC lower PF is boring as hell. They used separate buttons because they have it coded to play the upper and lower playfields simultaneously.
A jumper wire may be able to tie the two flipper buttons together and control both at the same time with one button. Only concern is that the lower flippers would be constantly active. Do the lower flippers disable if you are not down there like Black Hole?