Can I offer my pennorth on Gunter's manoeuvre and the control sequence used to produce a 'wing-over' or a loop. But first to answer the handling sequence question.
Apart from one occasion as below, I've only ever performed a full 360 degree vertical' loop at height .. say 1000 feet. I use the following sequence on the Enstrom 280c/FX.
A run in on the selected display axis using 30" MAP to achieve a 90 mph 'gate' speed. (Enstrom) Normal disc-flapback is allowed to bring the nose up for the first 30 degrees in the climb. Speed will be circa 75 mph - when aft cyclic is introduced while maintaining constant collective lever and yaw pedal position. At the 90 degree attitude aft cyclic pressure is tightened. I then look over my head for the horizon reference at which point collective lever is progressively lowered with further aft cyclic but - and it is a big but ... it is essential that a minimum airspeed above translation lift (say 40 mph) is showing on the ASI. Once the airframe has passed the top position, lever should have been been lowered fully to its minimum position (needles to remain joined) as the aircraft speed increases in the descent. Initially firm aft cyclic can be used but as speed once again approaches manoeuvre entry speed ... standard flap back brings the nose back up to the horizon which is assisted by appropriate aft cyclic.
I have flown these manoeuvres with a G meter fitted which has never recorded a zero G reading. Maximum positive G was recorded at 1.75. Also, and before embarking on the manoeuvre, I flew many sorties with an 8" balsa wood extension gaffer-taped to the dorsal fin and with 'tell-tale' markings on both the M/R dampers and blade up-stops.
Going back to the loop sequence, if 'gate' airspeed is lost as the airframe approaches the highest point in the manoeuvre, right yaw pedal can be used to convert to a 270 degree or 360 degree 'wing-over.
For actual displays commencing at around 20 feet, I use what I call a '270 degree' loop running in on the 'B' axis to the crowd and completing the manoeuvre flying parallel to the crowd line. In essence this is a wing over/torque turn. I did perform two full 360 degree 'wings level' loops using an Enstrom F28-2 at the 2004 North Weald Air Fair which was filmed and is now included in my scholarship DVD sequence.
Studying Gunter's unhappy manoeuvre, I feel that he did lose airspeed and translational lift at the top of the sequence and was probably pushing forward on the cyclic in the vertical nose-down position in the descent, but rapidly changing to hard aft cyclic when he realised the increase in speed was costing too much height. I watched him make that mistake at the 2005 Rouen WHC event but on that occasion he did succeed in pulling through safely although only missing the surface by a very few feet.
I suppose I should close by saying ... please don't try this flying without experienced guidance.
Take care all. Dennis Kenyon.