There was a lever pivoted with the bellcrank that had a little weight on the outboard side. The switch could disengage the bellcrank from the lever so the bellcrank then did nothing. The pushrod was driven by the lever.
When the model turns into the wind, it slows down and the lever moves forward as a result, giving a touch of down elevator to counter the tendency to climb. Going downwind the model speeds up, the lever moves rearward and you get a touch of up elevator to counter the drop. It actually got patented!
That little Cessna 150 turned out to be a great flyer. I just lucked into a super combination of balance and aerodynamics. The other two in the series, the P-39 and Comanche flew fine, but just didn't feel as good.
The models were quite small, and really only needed a .020 for power. .049s were much cheaper because of the volume of production. The solution was to design a really, really bad prop to get rid of excess power!