Something we've done that seems to help participation is to start timing events like loops and rolls after the contestant gets to a comfortable altitude. They decide when to begin and time starts when the first maneuver starts. It frees the less experienced guys from the need to do things down low as they would need to if we timed from takeoff.
Also, we've learned not to include engine starting in timed events. The rush makes it just a little dangerous. If you let everybody get started and adjusted it cuts down on taking off too lean or with the Ni-Starter still attached.