RE: Adding weight to planes
Knowing nothing about the Giant Big Stick I did a search for the specs and it seems the weight range is 13-15 pounds. Adding 1 pound to the minimum weight means the weight has increased by 7.7% so the wing has to make an extra 7.7% lift which means it has to fly faster. But lift increases by the square of airspeed so to make an extra 7.7% lift it only needs to fly 2.8% faster. In other words, if the stall speed at 13 pounds was 20mph then at 14 pounds it'd be 20.56mph so basically you'd never notice the difference in stall, take off or landing speed.
In flight, if the 13 pound model could pull a maximum 10G turn then the wing is capable of producing a maximum possible lift of 130 pounds at whatever it's maximum flying speed is. No matter how light or heavy the model is, that's all the wing can do at that speed. So if it weighs 14 pounds then the most G's it can pull would be 9.3 (130 pounds lift/14 pounds weight).