Actually Rick, Spitfire pilots will tell you that the real thing has an innocuous stall, and the full size has 2.5 deg washout too. The FW190 has three deg washout, a higher loading and a harsh stall, enough to limit manoeuver margins. Which is why the Spit can out turn a 190, the pilot can fly a Spit into the stall with confidence, a 190 will stall so deep and quick it will flick into a spin the other way, and end up being the target. Against that, of course, the 190 had magnificent ailerons and could change direction fast enough to pull the wings off a Spit trying to follow. But in general, the narrower the tip, or steeper the taper, the more likely you will have 'Tip stall', and the easiest way to reduce the effects is a bit of washout. Straight, non tapered wings of moderate A.R. don't need washout, as the reasons given, ie stall from the root to the tip. So for most sport and trainer type R/C models you can just build them flat and not worry about the stall propagation at all.
Evan, WB #12.