L2 I'll give you the benefit of the doubt.
And again, the L2 has mass, that needs to be accelerated to keep the same IAS going into downwind. See post 27 in this thread
You keep making good points that everyone accepts about ground speed illusions, being on the wrong side of the power curve, and the energy impact of windshear (gusts). But then you exhibit this confusion about acceleration.
This acceleration that you feel the helicopter has to undergo when turning downwind is relative to what ? Early on you seemed to think it was relative to 'mother gravity', and hopefully I skewered that when I said that the gravity vector is not going to change over these distances, it'll still be straight down. Now from the quote above you seem to imply that the acceleration has to be relative to the air, but why ? Especially if you accept the model helicopter in the train scenario.
Your airmanship views concerning the downwind turn are smack on the button, but your physics is a bit rusty.