My son's 11'th birthday today and this was his present. Apparently lego still ships these with a 1x9. He asked me to find his mistake when the elevators wouldn't go down, but I couldn't. So he replaced that 1x9 on his own with a 1x11 before I found this thread. Glad to know that's an acceptable fix. He used the 9th hole for the rubberband and the 10th for the string. Had to add an extra piece to have those attach to different points. That mechanism is a bit weak, but definately not a bad model. It's taken him over 3 hours so far and he's having a lot of fun with it.
Todd