At this time, I can't locate all the details. The airfoils used are Selig 8036 and 8037 airfoils, with the 8036 at the root and the 8037 at the tip. While the various Top Flite Gold Edition warbirds have intended maximum design weights, we've had people tell us of models that we'd consider grossly overweight still have good handling. These particular airfoils tend to not have particularly-bad stall characteristics...in fact on the tapered wings of the warbirds, tip-stalling is much-reduced over airfoils used in previous models.

One of the .60-.90 size models calculates out to a little over 32 oz/sq. ft. wing loading (713 sq in area, 10 lbs max weight). In the past, this was considered rather high for that size model, yet it handles very nicely with a very reasonable stall speed. Even grossly overloaded to about 13-14 pounds, the stall was reasonable, given that it was at a higher airspeed due to the weight.

Yes, the airfoil change from root to tip may be the main reason for good handling, but it works and works well. That's why it's used on most of the warbirds (the only ones that don't have that airfoil were designed before they were developed).