i use a dual purpose method. take a length of cord twice as long as is needed to hang the knife round your neck. slide it through the belt loop, pull a load of it through and go through the belt loop again. then tie the two loose ends together.
you now have a neck loop that is twice as thick to spread the load. when you want to hang it baldric style, (not the blackadder baldric) you simply lift one loop only over your head and shoulder, the other loop pulls down to nothing and you have instantly adjusted your lanyard to suit going over your shoulder to hang under your arm.
the other advantage of this system is that you can wear your knife very comfortably and withing easy reach, if you come across some other walkers in the woods, it only takes a second to pull the shortened loop up over your head and the knife is tucked discretely away under your jacket where it won't scare anybody.
once upon a time, suffering from an aching neck, i thought it would be a good thing to use bungee cord with it's built in shock absorbing properties to hang my knife on. all well and good till the lanyard got caught on a branch where it stretched longer and longer. i turned round to see what it had caught on, just in time to see the branch give way, launching the handle straight into my gob at a hundred miles an hour. :shock: something best ovoided. many production neck knives are sold with ball chain lanyards so you can't hang yourself if the lanyard gets caught on something. jst a thought to bear in mind.
cheers, and.