I vote to border it just like the sashing! Your hst's look great. You are doing a great job with your challenge using up your blue scraps.
I just love the sailboat block you have chosen and have enjoyed seeing the varied background fabrics you have chosen. My niece is having a baby boy in Nov. and I was searching for a quilt to make. You have inspired me to try the Sailboat block. Did you follow a pattern for the block that you can share?