I usually wear a size nine shoa and just...
I usually wear a size nine shoa and just received my size 9 chacos. There seems to be a lot of room at the back of my foot. my heel doesn't sit all the way back in the heel cup. Should I exchange for size 8 or do I just need to work on the strap adjustment?
You should have some room around the edges of your Chacos. With your heels and toes right on the edges, your feet are more susceptible to trail damage. If you have more than 1/2" or so, however, you may want to size down. I'm a size smaller in Chacos than I am in street shoes.