42 inches would be a comfortable distance.

We agonized over this when we were laying out our kitchen. We had seating on one side of the island and it serves as the main travel aisle when coming into the kitchen from the outside. We ended up putting 34" between the prep side of the island and the cabinets. I know that is less than standard but having worked in this kitchen for the past 15 months we've found that it works well for us. If you have some large boxes (like from appliances) place them in the space and see how it works for you.

Gorgeous kitchen Kevin! What size is this kitchen?

The entire space is 13' x 26'. Approximately 14' of the space is kitchen (cabinets, counters, etc.) and the remaining area is the eat in area. We had the pantry wall, on the right side, cut down from 24" to 16" so the travel aisle would be wider, and we still have plenty of storage there.

Great space in your kitchen! So sink aisle side is 34" countertop to countertop and still enough space for passing through and working comfortably?

How long is your island and how many inches of aisle do you have on stool side? Thanks!