I don't want to use the lower brass nock as it wears my tab.  What is the best way to handle this?  Just put some serving in this location to keep the arrow up against the top nock?  Is there a better way?

cj,  I hate those brass nocking points.  I'd rather shoot without a NP than to use one!  I use string serving but I know some folks like dental floss.  If you're going to put a second NP on, leave it a little loose to the nock.  That is it should not actually touch the arrow nock.  You will probably find that adding the lower NP will change your arrow nocking position too and you'll have to relocate the upper NP.  Long way of saying that if you add a second NP plan to retune the bow for proper NP.

Byron Ferguson demonstrates tying on a nock in his video "Become the Arrow."  I'm not sure what he uses, but I use FF string.  He ties a simple overhand knot around the serving, then ties another overhand knot on the other side of the serving, and continues alternating back and forth 5-6 times.  Then I believe he makes the last overhand knot into a square knot, at least that's the way I do it.  Then cut the loose ends off to about 1/8" and burn them down to the knot.  After doing a few of them, I got the hang of it and now just tie them on tight as I make them.  I make them so the arrow nock has a little play to move up and down, probably less than 1/16".  I regularly bare shaft tune all my arrows, and haven't found that I have to re-tune if I'm adding a tied-on nock below after I've already tuned with a brass nock above.

That makes sense.  I don't mind the top nock being brass as the tab never touches it.  That's the way I tie on my silencers McDave.  Maybe if I wax the serving string before tieing it that it should secure it even more.

O.L. Adcock suggests that the the arrow nock fits easily between the nocks with no up or down play. That's how I have my nocks set.