Moment of Panic - knocked out

Hi
   
I have recently bought my lovely Syrian Hamster, he's just 6 weeks old and in possibly the most excitable and energetic creature i've ever seen!
   
The cage is on two levels, main area at the bottom and the petting area on the top connected by tube. He has a habit of sleeping in the top curve of the tube and well, last night he fell down and hit his head on the bottom curve, slid out and laid motionless on the bottom.
   
Panic set in as my girlfriend and I tryed to nudge him and yet he still didn't wake up, he seemed to be unconcious but the first fear was that he had died (dramatic, i know, but still)
   
Anyway, a few seconds later he woke up and looked a bit confused, so i put the water tube to him so he could drink without having to move.
   
He seems ok now, (back to his crazy ways) but still insists on sleeping in the top curve.
   
We've put bedding down on the bottom curve so if he falls it wont hurt but I'd really rather not let him fall again. Is there anything I can do to get him out of the habit?
   
Thanks
   
Mike