I think when it comes to something that is for sale, the manufacturer goes for the safe number. Not a pattern plane but my old "U Wish it Could Do 3D" 46 was way underpowered with a 46 or 70 engine but they were worried that people would overspeed the planes and they would blow apart in the air. I put a 60 two stroke on it and it was ok. 60 size need 90s. 90s need 120s. The pilot has to know to use the throttle and not hall around doing speed passes, which is not what the average modeler does.