Minimum chain length should be the length of your boat especially if you are ever going to overnight. Personally I doubled it as I don't ever want to wake up on the rocks.
Also, I second Pelagic's comment about 8-plait rode. I am in the exact same boat (pun intended) and you have to be a contortionist to get into a locker full of 3 strand rode to get your hand up to where you can pull the last 100 feet or so of rode in off the front slope of the locker.
Also, I second Pelagic's comment about 8-plait rode. I am in the exact same boat (pun intended) and you have to be a contortionist to get into a locker full of 3 strand rode to get your hand up to where you can pull the last 100 feet or so of rode in off the front slope of the locker.