I have practiced building light airplanes for many years now but in control line. And it has filtered over to r/c now ecspecially with 3d. The lighter the plane the better it flys ..PERIOD..
When building from a kit, start by weighing everything before you start any building at all. The engine, muffler, all bolts and hardware, fuel line, tank, wheels, landing gear, wheel collars, fuel dots, spinner, prop, I mean everything. Once all of these items have been weighed you will know how much weight you have left to build the airplane to fall into the target weight. So if you are building from a kit, now you can start replacing the wood with contest grade light. If you are scratch building then I hope you are already using contest grade wood.
This really works and you will notice the first entire plane you use this method on will be one of your better projects when it takes off the first time.. Hope this helps some of you, BAD ANDY