Under 80k doesn't really count for pain. You really need to be doing 70mi+ before you start to notice painful setup problems (unless they're really obvious ones). I'd not suggest doing 140mi out for your first ride and doing it fixed doesn't help because when you are in pain it's that much harder to stretch and stuff. You need to factor in navigation and breaks as well so with only 8-10 mile rides a day you're not really in a position to know how comfortable/uncomfortable your bike is, nor how much to eat and drink. Give it a shot but have a bail out option in mind (train, etc).