There's no such thing as a small part. There are just small actors.
All good work requires self-revelation.
Over-length is one of the things that most often results in the destruction of the movie in the cutting room.
It's art. It's commerce. It's heartbreaking and it's fun. It's a great way to live.
There are no personal revelations other than feelings arising from the work itself
The varying physical characteristics of the actors may also necessitate changes. Sean Connery is six feet four. Dustin Hoffman isn't.