Not Easy To Answer...
as what might feel secure to me may be uncomfortable to you. Also each mooring has so many variables. Is there a lot of local traffic by your slip? What are the prevailing winds in relation to your slip? What is the tide range? Are these permanent dock lines, or are you going to take them aboard with you? At the very least, docking lines should match the stresses place on them, so for your model 3/8" 3 strand nylon (the best for shock loading) would be a good start. If the boat surges back and forth I would include "spring lines", one run from the stern forward and one from the bow aft to the pilings (see West Marine catalogue for a diagram). In addition to the spring lines, a bow and stern line too. Watch out for chafe, anywhere in the system. If there is, add chafe protection, such as a piece of split hose, or leather. Make them long enough that tidal ranges are taken into account. If these are to be left tied to the piling rings I would add an eye splice for the boat cleats and push the eye through the cleat and back over the horn. As far as the knot to the piling thats personal preference, but you can't go wrong with a bowline. Don
