At about 8 ft wingspan, models take on more man carrying traits than the model ones. Three foot wingspan planes have a certain characteristics, from there to five foot change some, five to eight moves some more, and eight and up start acting with their character. You have to get the plane big enough that the ambient surrounds are not amplified. Small model’s power available tends to hide a multitude of sins aerodynamically. A model airplane will fly; how it reacts for data collection requires a lot that would compromise it as a model airplane.
Yes I agree...and at this ( 8 ft or more spanning ) size you start to see many construction details better as well.
I have done several smaller models too just to see how it glides...and looks...to get a feeling that you cannot get from the drawings.