During banner pickup the tow rope became wrapped around the release hook and the pilot was unable to release the banner upon the completion of the flight. Landing with a right crosswind and the banner still attached, the pilot was unable to control the direction of the airplane as he slowed, and the airplane departed the runway to the left side, and nosed over. The banner attach point was a hook on the end of a rod, which was attached to the main landing gear, which is forward of the center of gravity. This made directional control very difficult if not impossible as the airplane slowed. According to an FAA inspector familiar with banner towing, rope is more susceptible to twisting around the release hook than metal cables. In addition, he said that tailwheel mounted tow hitches are safer than those mounted on the main landing gear. Additional interviews disclosed both tow hitch systems and rope are in common use for banner towing.