We've used Royal Canin Yorkshire 28 for years, along with raw meat (from Darwin's Natural Pet Food -
http://www.darwinspet.com ) for both Yoda and Winky. Yoda was a little heftier when he was younger, but that was mainly because we gave him a little too much in terms of treats. They are both within the weight range for Yorkies. And they both only poop once a day.