I had the same problem on mine, tried all kinds of tightness on the blades, from so tight it almost stripped the screw holes out to so loose if you sneezed on them they would move. It turned out that the rotor head wasn't flat. I pulled the blades off,then the rotor head off the heli, looked at it eye level and one side where the blades mounted was bent down some, so I heated it up ever so slightly with a lighter, and bent it back perfectly flat and held it under cold water until it was completely cool, slapped the blades and rotorhead back on the heli, spun it up and there was still a little vibration, but those went away when I balanced my blades. But as far as blade tightness, when I fixed the vibrations, I run them very loose, to where you pick the heli up by the tail and they fall to the nose of it. Still no vibrations and it will lift off like a rocket.