LOL...Some yorkies are MONKEYS....and they do have tops for X pens....if he's already climbing then sounds like you need one....
and if you think he'll get over his 'climbing urges' ...go see Cheri -
http://www.yorkietalk.com/forums/sho...t=37139&page=1 
she was the same way as a puppy...she climbed on things Chanel never dreamed of
and I BET he had a great time with his freedom...cute story
