I think that user-friendly wing loading is largely a function of the airplane's size. I would hate to fly a 24" model with a 20 ounce wing loading, but some 11 foot wingspan, 64 ounce wing loading UAVs we built for the military were *****cats. Taking this to a ridiculous extreme, a full-scale radio-controlled Boeing 747 would be very easy to fly, since it would appear to be glacially slow, giving the ground-based pilot lots of time to think, despite a wing loading of over 100 pounds per square foot. For the same apparent relative speed, it would appear that wing loading could vary as the square of model size. If you double the size, the model will take the same time to fly its own length, while flying at double the stall airspeed with four times the reference wing loading. An interesting subject.