LAX shuttle question

[blynn]

We have ridden the Disneyland Express Bus a few times on past trips, and it has worked out fine. For this trip, in looking at their schedule, we will have only have 25 minutes from the time our plane lands (at Terminal 1) to when the bus will pickup and if we miss that (we will need to collect luggage) we would have to wait another hour which we don't want to do. Often planes land earlier than the scheduled time, so we are hoping that we will have enough time. However, if we miss the bus, is it possible to go over to where Supershuttle picks up and see if there is room in one of their vans? I have read how they continue going around the airport until they are full, which leads me to believe that not all passengers have prebooked with them. Has anyone ever tried to ride Supershuttle without prebooking?