Death of the 13.5m class?

If this is "soaring," then no external power or induced thrust should be allowed. Start the engine, turn a prop (or turbine, or compressed air jet, or stick an oar out the window or whatever) and you are now a powered aircraft. In competition, the flight STOPS THERE. (Just like the OLC.) No exceptions. If you elect to augment your flight to make it home when getting too low for comfort and do not want to accept a landout, too bad. The scoresheet should reflect that you decided to terminate soaring flight at that point.

Also remember that virtually ALL external power sources (Reciprocating engine, Turbine or Electric CAN fail. And the insidious "Emergency Algorithm" dictates that it will most probably fail at the absolutely WORST time, i.e., too low over bad terrain when you have not previously selected an appropriate landing area and planned how to get in to it safely.

An auxiliary power source is a neat thing to have. Just remember that it is NOT a "Safety" device. It is best if you just treat it as a way to avoid inconvenience. Betting on it to save your sorry butt in a competition (or on any flight) is just asking for trouble.