Hickry,
I may be able to help here. Below is an easy way to do it assuming you're not shooting with a tab. (no stitches to count to know exactly where you shot it from down the string)
Step 1: Determine what point on distance you want. (for this example, lets assume 25 yards)
Step 2: Apply your brass fixed crawl nock on the string roughly 1 inch below your arrow nocking point.
Step 3: Stand at 25 yards (or whatever point distance you decided on in Step 1)
Step 4: Address the string at the brass nock down the string, Draw back, stick the tip of the arrow on the target where you want it to impact, and shoot the shot.
Step 5: If your arrow impacts where you're aiming, then you're done. Then move on to mapping your gaps as seen in the film. If you hit High or Low, move on to Step 6.
Step 6:
Arrow impacted high: Loosen the brass nock, and move it a touch more down the string. Then Start again at Step 3.
Arrow impacted low: Loosen the brass nock, and move it a touch up the string toward the arrow. Then start again at Step 3.
It is a little bit of an iterative process, but you should be dialed in within 2 or 3 moves of the brass fixed crawl nock point on the string.
PM me if you have any further questions as you continue to try and find your fixed crawl position.
Thanks!
Matt