When a plane takes off with the wind the wind will actually push the plane down and at the time of lift off it will push the tail down increasing the angle this creats a stall situation
This is NOT true.
Once the model has exceeded 10 MPH on the ground speed the relative wind is no longer a tailwind component. Thus NO wind is hitting the rear of the aircraft pushing it down. Saying this your rotation will still be 15 mph indicated airspeed and 25 mph groundspeed.