I have towed on several occasions(once about 15 miles of steep whooped-out trail)and the best technique we found is: NOT ON THER SIDE!!!(how humiliating)
Use a long enough rope for a 12'-15' gap and tie it to the cross bar under the hood at the nose of the rig and the bumper of the towing rig(snowmobiles are good for something, lol). Have the more skilled rider ride the towed 'Hawk out with the less skilled rider keeping steady on the gas of the towing rig. If the tow-er is steady on the gas, the tow-ee is able to get into the "groove" of the speed and handling of the towed 'Hawk over the bumps and turns. If the tow-er is herky-jerky, the tow-ee will never get stable and fall over, often. The steady speed also means less braking from the tow-ee to keep the towline tight and an over all smoother ride.
Don't tie the rope to the ski or forks as it doesn't allow the ski and fork action to naturally control the 'Hawk...