There have been numerous articles written recently that it takes 10,000 hours for a person to become an expert on any subject.  I have little doubt that I have exceeded that amount of time (several times over) with model aircraft over the past 50 years of interest in the hobby.  Yet I have never built an airplane with a 4 cycle engine, even though I own a new YS .91AC.  I have not built any model with gasoline power, or an electric (even though I am a degree'd Electrical Engineer.)  I have flown control line, free flight and almost every form or nitro powered RC with a bit of slope and thermal tossed in.  So while a pilot might be very skilled with 40 to 90 sized models, he can get into very serious trouble trying to fly a giant scale model using the same techniques.

In other words, even the experts have weakness.  Perhaps a great example was "Sully" the airline captain that landed in the NY river.  Fortunately he also flew gliders.  An expert without that extra skill set might not have performed as well.