Bushy
The structure around the engine is a fairly deep (chord wise) box section into the wing, within a short distance span wise of the fuselage attach and carry through point. I would be surprised that substantial untwisting of the wings could occur within the rated ultimate load of 6.6 G's.
If significant twisting did occur it would then tend to unload the lifting ability of the wing and hence reduce the G load. But it would need to create massive distortion and skin buckling. Momentary heavy negative loads associated the inertia of heavy landings would, I suspect have shown this as weakness very early in it's history. Additionally with the torque effect created in the same area from landing and braking loads on the relatively long U/carriage legs attached to the same structural area. This is probably an area of high surplus structural strength.
I would also assume (?) that the wing was statically loaded to verify ultimate loading and that at least sound mathematical modeling was done to determine the twisting moment of the forward of the CP engine mass. I don't know, but I figure that if the factory went to the trouble of static testing the main plane then it would not be an overly onerous task to load the engine mountings to verify the bending moment at the same time.
As one who makes a dollar flying, among other types, the lovely old Shrikes in low level ops, I look and listen carefully to matters of structural integrity for this type, whilst always keeping the fingers on one hand firmly crossed.
M