Just for fun...In theory an eliptical wing (ie like a Spitfire) stalls at the same time along its entire length but I suppose the Spitfire wing is not a perfect elipse thus the need for washout?
Also, lift/drag are effects not causes. I think a wing stalls at a specific AOA due to delamination of the airflow resulting in drag/loss of lift. True?
My experience is washout helps and scale washout is probably not aerodynamically ideal on a model but still helps.

PS. probably should have read this thread first before posting my dumb "Flaps and tip stall question".
Late night brain fade![:-]