RE: Diving on downwind?
Definitley an airspeed issue. That is all I can tell for sure.
When turning from upwind to downwind, there must be an increase in ground speed in order to maintain level flight.
Say that your plane is flying 60 MPH. The wind is 10 MPH. When flying up wind (level flight) your ground speed will be 50 MPH.
When Flying downwind, your ground speed must increase to 70 MPH to maintain level flight!
A 20 MPH (ground Speed) difference between flying upwind and downwind...... Well, theres your problem!
Doug