From the above report
The lack of precise evidence concerning the pilot's intentions and G-BVNA's flight path and speed after it turned inland makes it impossible to define the combination and degree of gust loading and manoeuvre loading which caused the failure of the wing. However, two related aspects may be relevant.
Firstly, although the workmanship in G-BVNA appeared to be of a good standard, a number of experienced aircraft engineers commented on the design of the wing structure. One observation was that, with the main wing spar not occupying the full depth of wing, the leading edge structurewould make little contribution to the tors ional stiffness of the wing and to the stability of the main spar. Another observation concerned the wing ribs, which were of simple 'trapezoidal' construction and appeared to have low in-plane stiffness. As the AAIB have not been able to contact the original designer, it has not been possible to discuss with him the structural design and whether, the static load test in Hungary was with a wing identical to that in G-BVNA.
i.e. hard to say... there are probably a lot of planes in this category which might not be that hard to break.