I have a few TC N.E's one of which us the Greyhawk in. 54
It shoots the traditional projectiles whether or not they are the planet shaped ones or the ones that rhyme with monical.
I tried sabots (TC yellow sabot and 250gr lead pistol boolit) from my 50 NE and found then to group poorly at 50yds with various charges .
Maybe they'll work for you??
Just to add; I read on another forum that the 54 cal sabots were much thicker than your regular 50 cal ones. In some cases the bullet and sabot would stay together until it struck the target.
This discussion that you brought up "Elbow " has given me the urge to do some further R&D as I have plenty of 250 & 300gr cast boolits to try