I just had a new string put on my bow and I also installed a string loop for the first time. My local shop told me to keep my nock on and put the top of the loop on the outside of nock (above it) and the bottom one below. With obviously enough room to nock the arrow on the string. My question is, do I need to put serving between the bottom of the loop and where my arrow nock is or just let the loop kind of "snug" up against the arrow when it is in position?

Make sense?

You really dont even need the knock there. The tension on the string loop will be more than enough to prevent it from shifting unless you purposely loosten it.

I put a clip to hold mine in place once i got my bow tuned. If you accidently hang the loop on something, like a limb, it will slide on the string if its not secure.
good luck

I have never needed to use a nock with a loop. It will tighten down on your serving and stay put. It also makes tuning a lot easier too. You just rotate the loop around the string to move it up or down a 1/16th of an inch at a time.

i recently bought a bow with a loop and i use it and it seems to work fine, the previous owner used the loop and had success

How I have mine set up right now. I can't move the loop down any or I would, but this is the general idea.