Well watch the levels like a hawk, most hardcore screamo bands want a lot of distortion, you know in a digital world that sucks.
Depends on how many tracks they want to do, are you charging them good $$ - or did you state an amount of tracks you would do for them. Only asking is because you can layer tracks with less distortion and still make them sound huge and loud. At least it works for me.
Are they bringing all their own equip, or can you sub in some midi stuff for them? Like drum kicks in midi or wave files can help a lot too.
Like I said watch the levels, I know a few hardcore guys and they are in my eyes NOT real laid back dudes, so they have a lot of wanting OVER THE TOP preformances even in the studio concept. Good luck to you..