Air breathing engines (as well as RAPIERs in rocket mode) drain fuel evenly from all tanks, regardless of crossfeed or staging. What this means is that you don't need any fuel lines anywhere ever and that fuel will drain from your payload if you have any, so be sure to lock your payload fuel before launch! Also if you are having trouble landing if you land on the field next to KSC, you get 98% recovery for a much much easier landing.