I agree with wisguy and smartkid222.
More specifically, it would be very difficult to get a rubber powered helicopter to hover (cruise) for any significant aount of time. The ascent could be slowed, but only at the expense of shortening both cruise and descent. In addition, to keep the Helicpters event competitive across the country, any bonus for a no-touch fight would have to vary depending on the ceilng height of the flying site.
Friction, cannot suspend the weight of the helicopter from the ceiling. Unless the helicpter is stuck, only the lift of the rotor(s) can do this. Timing in such situations is easily accomplished by using two stop watches, as wisguy explains. There has always been a luck factor in flying competitions where the aircraft are designed for free flight.
The Helicopters event has only been official for one year. Next year, the rule changes should be minimal, e.g. change the max rotor dimension, miniumum helicopter weight, and/or max rubber weight to prevent students from handing down their 2011 helicopters. This would still allow returning students to build on their knowledge base in the Helicopters event.
If the National SciOly organization wants to encourage experimentation in the Helicopters event, try a bonus of doubling the flight time of a tandem rotor helicopter, i.e. one that has a pair of separate rotors that spin about different axes spaced apart at least the max allowed rotor dimension. Imagaine the challenges in building and trimming a balsa wood stick version of the Chinook helicopter.