I soloed my trainer,A Balsa USA EZ 100,in eight flights and went on to build three more before I moved on.I hacked the crap out of those planes before deciding it was time to move on.The last one had a Rossie 60 on a pipe and would go out of sight as soon as it had enough altitude for the elevator to clear the runway when rotating.In all likelyhood,i had a problem,kinda like a babies security blanket.On the other hand,I soloed a one to one Cessna 152 during my seventh lesson.Go figure