I just checked the Atari ST port of Slap Fight, and indeed was gobsmacked by the ammount of stuff they got wrong from the arcade game.
For starters, the aspect ratio nearly kills the game. The game seems to be well programmed, but there's a lot of stuff done wrong that could easily be done right.
Slap Fight is such an old, simple game, there's no reason it shouldn't be a near perfect arcade port on Amiga. Geez, even on Atari ST, it should had been a near perfect arcade port... looking at the ST game, I see no reason why it wasn't a proper port of the game, instead of butechering a lot of stuff for no reason.
The arcade game is awesome, even being such a simple game