I've always use Singles to teach correct lines, easier to work-train a dog on factors with only a single, setup the triple run them singles. A week later perhaps come back run it as a triple. I know my dog can count, and has memory, but she won't always take the correct line to the marks. She choose to proved this in a final series last weekend, knew exactly where every bird was but choose to "do it her way". I believe she will be seeing nothing but long technical singles for awhile .