We are building a quadcopter using the hobbyking x666 frame and an arduino due. the wireless controller we are using is the turnigy 9x. After tuning it wrt roll and yaw, we took it for first test flight which didn't go so well. It wasn't stabilizing itself for sure but one other problem we encountered was that we weren't able to determine the hovering thrust of the quad. Increasing the thrust would take it up and decreasing it even a bit would just make it drop.
Is there a way to determing the hovering thrust?
Is this even the problem we shouold be looking into?
P.S. 'we' are a group of 4 students.