Hi!
After having flown the GP GEE BEE R-2 know for 3 years I have the feeling that the problems many flyers encounter with this airplane is building it too heavy and powering it with too big engines(Gas engines and bigger than 20c four-strokes)
If you just follow the GP instructions and power it with either a 15cc two stroke or a light 20cc four-stroke engine and building it light, removing parts and making lightening holes were ever possible, your chanses of having it survive the first flight will increase dramaticly.
I fly mine with a 15cc two-stroke engine using an APC 15x4W prop and it weights exactly 5kg (5000g)....that's under the GP recommendations...but it's still a handfull to land, but it flies real well and is very aerobatic.