Gross weight has to do with the rated max G-load on the wings, but also the landing gear capacity, engine size ect.... It's not just one thing. Clipping the wings on a model-4-1200 will allow a high G-load on the air frame ( mathematically speaking), and that is what I am doing to raise the gross weight to 1250 lbs on mine, but I also installed upgraded aluminum landing gear and a more powerful engine to take the extra load up in the air, and put it safely back on the ground again.

So what's the limiting factor on your model 2? Probably Engine HP for a decent rate of climb, as I doubt you are going to break the wings or landing gear (though I have heard of breaking off the bungee attachment on a hard landing, collapsing the gear). Anyway, if you modify the plane for a high gross weight, you have to run it past the FAA, and they will probably issue you a new pick slip with the increase rating listed, along with some test hours (5 or 10), but their response seems to vary with the particular office you go though (my local office does not seem to care about prop-planes, as they are in Wichita, home of the big planes).

Hope this helps
Roger