There is a huge hazard when string walking though. If too much concentration is put on the aiming and not enough on the "back of the shot" -- follow through -- groups will grow and other bad things can happen. I discovered this the very first timme I tried it. Then I realized what I was doing. Once I figured out that I need to visualize my sight picture before (or as) drawing my eye will form that relationship without my mind spending much time on it. For example, at 30 yards the point of my arrow needs to touch the edge of the body behind the shoulder.
Then I can concentrate on keeping the bow arm and drawing back muscles active so follow-through will be fluid. It makes a huge difference - beach ball groups at 30 yards vs. half a paper plate!
Now, every day (our season has been open 14 days) I shoot 10 arrows from my elevated (deck) perch at 3-D targets: 7, 12, 20, and 30 yards (once in a while 35 also). I usually shoot two each at the 7, 12, 20 and 4 at 30. The pair at the short distances are almost always top of the heart. The 4 at 30 will typically be 3 kills and one high liver (still a kill but not what I want).
I never would have believed I would use this system of aiming but for me, I love it. It is a great bridge from compound with sights back to the recurve.
Here's a quick way to try this. Three fingers under. Put your index finger under the nock of the arrow. Then mark the bottom edge of the index finger with your thumb and move the fingers below the thumb (you are now an index finger width below the arrow nock). Then you should be point on at about 20 yards. This is over simplication. If your nock locator is higher than 1/2" or if your arrow is protruding more or less than 2 inches from your bow, this might not be right on for you.
Imagine the point of the arrow touching the center of the lungs. Come to anchor, think about moving your drawing thumb to the shoulder as soon as you drop the string (follow-through) and ....?