Although I don't use a loop I've installed a few in my short 30 year career. Something I vary rarely see mentioned is the idea of putting string wax on the serving before installing the loop. When a loop is put on and tightened there is friction between the two materials which doesn't allow the loop to be as tight as it might get. Waxing the string reduces this friction and when tightening the loop with needle nose pliers, as mentioned, it allows the loop to pull tighter. This paradoxically, reduces the chance for the loop to twist on the string, or slide up or down.

The loop is not supposed to be used to align your peep though. What it is is a bandaid for string problems. Not enough twists or just plain lousy strings twist when the bow is drawn and this rotates the peep. The best remedy for this is to twist up the string and shoot it till it settles down or get a good set of aftermarket ones. One name----Gibblet.