The big lesson may be the impracticability of the large, rigid and heavy kites, at least by flying in circular figures.
An underestimated problem may be the significant kinetic energy as the kite descends, preventing it from ascending. Thus a wing like M600 weighing a ton and flying downwards at 50 m/s produces 1,250,000 Joule, added to gravity. And its speed upwards is lesser, so its kinetic energy is also lesser.
Perhaps kinetic energy issue during flying downwards phase can be mitigated by flattening the trajectories, using flat figure-eights kiteKRAFT fly-gen kite flew figure-eights.