the early 05 bipes could not glide. Spinmaster had them geared for 3+. You had to fly at max throttle all the time and you needed wind(think the f-16) and a flght of more than 8 minutes was exemplary. There was no glide factor, when let off the gas it dropped like a rock. I would say that the glide factor was 10/1. It should be obvious that I had one. A bunch of people bought them and started "fixing them" thats how the mods started. The first mod I saw was a professor type demo'ing his plane. He had what appears to be cassette tape tied to the tail, the ribbon mod(I still think silk is best). The next couple of mods were mono mods. Check online for AA forums, I don't remember which I was reading. To give you an easy understanding, the late 05's and the 06's have a glide ratio closer to 1/10. My thought is that the changed the formulation of the styro. Tim