I wouldn't worry about the weight being too much for your Chi to handle. I have 3 Yorkies, Jeter is my oldest at 13 months of age, he is also my smallest at 2 pounds 8 ounces. Axl is 5 pounds at 5 months old and Yumi Yasha is 3 pounds 7 ounces at 5 months old. They all play great together
and Jeter holds his own ground with them
( he thinks he is a Irish Wolf Hound at times)