What the last couple of posts say is correct. Imagine swimming in a river that is flowing. If you closed your eyes you wouldn't know the water was moving. This is what the model experiences in moving air.
There is no difference in thrust upwind or downwind.
A fan unit does not unload in flight it actually loads up slightly because the airflow increases and the fan has more work to do.
Cover one intake up and the revs increase. This is because the fan has less work to do.
I know this from IC Ducted fan days when I had on board tachos.
Also ask Stumax if you don't believe me.
It did suprise me because they do sound like they unload as they come towards you but it's the doppler effect.
Think about a motorbike coming towards you and then going away. The sound changes but the speed of the bike doesn't
Jim