Is ratatat actually coming on at 7??? I dont know your venue, but out here music doesnt start until an hour or two after doors. And if there are openers you should be fine to do both as well.
so trrue. immortal technique doors at 9 came on at 12. same with nas. i think ratatat would do the same. unless you have already accounted for this time
or if it is a free college concert. I went to Girl Talk in boulder a week or so ago. He was on at like 9.00 and only played for like an hour, super weak considering the artist.