I use both an upper and lower string nock for consistent arrow nock placement.

I'm wondering whether a snug arrow nock buys much here.  Any thoughts appreciated.

My arrows will slip off the string when pointed downward so they fail the  "arrow nock should be snug enough to remain on the string when hanging downward, but not too snug as to remain on the string with a firm tap" test.

Thanks !

Too loose an arrow nock will affect accuracy, since the arrow can wobble from side to side on the string, as well as possibly causing a dry fire if the nock falls off the string at full draw.  The old "arrow nock should be snug enough to remain on the string when hanging downward, but not too snug as to remain on the string with a firm tap" test is a good one to ensure that your nocks are not too tight or too loose.

I like a light fit,it will hold on the string and come off with a light bump.Too loose can make it easier for a dry fire and like said can affect accuracy.