Go for it. See both shows and there is a good chance Phantom will start at 5 :15. At Slave Play see if you can get an aisle seat and as soon as the play ends your on your feet and out the door. Walk down 8th Ave quickly and it will all work out for you. There is also a possibility that Slave Play may not appeal to you and leaving your aisle seat earlier will expedite the matter. Don't pass up the opportunity to see two shows. You'll regret it. As far as an aisle seat goes if you ask the house manager inside the theatre they are usually accommodating. I never have a problem in situations like this.