I have installed a kitchen island 54x38" and I am trying to find 4 stools. We love these stools (pictured) but I am not sure if they may be a little too big. The top picture seems to show that they are well proportioned for the table top size, but the lower picture shows that the two chairs extend beyond the base cabinet - is this "visually" a problem? The island is 54" wide so two 20" wide chairs fit, but the base is only 30" wide so pretty much any stool we get will extend past the base

For me, I would look at the countertop size as a guide, not the size of the base. The question you are asking can only be answered by you as it's just a matter of personal taste. If seeing the legs of your stool protrude out past the base of your island bothers you, they look for smaller, narrower stools. Otherwise, look at the island and stools as a whole package - if the one in the picture looks OK to you then feel free to duplicate the look, even with larger stools.

This is not a right or wrong thing, just a matter of what you like.

Jaybee: Thanks for the reply - the island in the picture is the one i NOW have in my kitchen (the one you helped me build by answering questions about anchoring and sub base supprt)...now your chiming in on the finishing touches! Really appreciate the advice (everytime).

No chair you get is going to push all the way in. A shallow rectangular stool would work. How do knees fit in this arrangement? If it works for you, it is fine.