Hmmmmm. Speed nocks might work. They're not made any more, but still available on the auction sites. They have a straight throat and a raised indicator that lines up with the cock feather. However, if you're going for speed, really doesn't make any difference whether you nock cock feather in or out. Howard Hill, who was pretty quick from quiver to string, nocked his arrows above the string nock. He felt it was the fastest way to get the arrow on the string and in position. Have fun.