Any port in a storm
Knowing where the slings go is a good idea -- we almost took our out propshaft hauling the boat this fall. Many people would be happy to sell you a sling decal kit for $19.99 (A $587 value!!!) The kit consists of a permanent magic marker and a piece of cardboard with a diamond shape cut out in the middle. You line the top of the cardboard up parallel with the top of your toerail so that the diamond shape is near the top of the hull topsides. You then trace out the diamond shape, using the cardboard as a stencil. You may want to select a color that contrasts with, but which is complementary to, your topsides color. Maybe the same color as your cove stripe or waterline? You can color in the whole diamond shape, or part of it, to make it "customized". (This does not cost extra.) Repeat for the other three locations the slings need to go, making sure they're even on both sides of the boat. If you've got a dark hull that won't show the marker..... use a piece of tape, or file a small notch in the toerail. It beats wasting time in the store when you could be out sailing.