He's lovely! A very handsome boy.
Oohhh, somebody with a Duna Fun! I have one of those, it came with my adopted hamster, Herbert. You could always extend his cage as said (is your Duna Fun intact? I had to wire mine together as it was falling apart when it came to me! :P )
This is what I have done with Herbert's cage:
(I got the Rody for just £9 as it was cracked in the corner)
Herbert negotiates the tubes with no problems at all.