This is the board I have been using. It is 4 inches to the top nail in the triangle for the dropper loop. Smaller the triangle the smaller the loop , but you can also change the size of the loop by the direction you pull the two ends. For example, if you are tying by hand and the loop is in your mouth, you normally pull the 2 ends side to side. But if you pull them down you will have a much bigger/longer loop. I know this probably sounds weird but I can't explain it better than that.
A video to get an idea.
http://youtu.be/X5sLQH_N3BM
