Ah! Sorry for the belated reply but I wanted to say thanks, cos the American-voiced boys in this canon are all around the Young Man's age (20, 20, 22, 25 I think) and they use 'dude' mostly, but sometimes 'buddy', and the rules around it are a bit opaque. So this is useful info! I'm just looking to avoid awkward howlers that aren't gonna be obvious to people from outside the culture, like Lucius Malfoy using the word 'bloke' or Ron saying 'chap' in Potter fic.