I built one and it sat engine less until my uncle found a 1972 OS-MAX H in his basement. Has been one of my favorites for several years now. It really scoots along. I echo the sentiments on the balance. I use the recommended throws but find if I pull to tight of a loop, it will snap out. So be careful there. The initial hand launch is a bit scary, but once you get a hang of it, you will be fine. I also run 30% fuel so I get a smoke trail just in case as this bird moves. Of course I run 30% in most everything I have.
Also, make sure you have a big contrast from top to bottom. You can get disoriented fast with this one.
Just hang on and have a blast! Great kit for the $$$
Jason