This is great in theory.  There are a few design elements I would add.  My cat is average size and likes to take running leaps onto the tower.  If there was one more leg on the first level, it might not wobble as much as it does.  I've even tried tightening the bolts and it is still a little too precarious for my taste.  My cat loves the lower levels but I think he might be just a bit too big for the higher ones.