Miloh:

Great Planes lists their Extra 330L with a 100.5" wingspan as a 1/3 scale. If accurate that means the full size plane has a wing of 25' 1 1/2" span. And the "Patty" Extrra 300S at 1/4 scale is 78" span, that would make the full 300S a 26' span.

So now you have to decide how big a plane you can handle, figure the percentage,and go from there.

Bill.