If your engine rpm is constant or nearly so, rotating mass of the engine,clutch and drive train is essentially irrelevant.
The only time rotating mass becomes and issue, is if the rotational speed of the engine and drive train is changing very rapidly (like in a drag car or a sports car accelerating out of a corner).
At near terminal speed in land speed racing where engine rpm take seconds to change a hundred rpm it means very little.
Reliability under continuous load trumps the ability to change rpm rapidly.
Larry
