Not technically a baldric rig, but I have a sling that I use to carry a couple of my bigger hand axes, one has a 20" handle, the other has a 25" handle, the sling is made of 1-1/2" wide cotton webbing and has a paracord loop on one end that fits through the lanyard hole on the end of the handle, the other end of the sling has two paracord laces that tie to the axe head where it meets the handle, the GB small forest axe weighs about two pounds, the other is a hunters type axe and weighs about 2-1/2 pounds.
Both carry very well, and the sling allows several ways to carry, across the chest, on the side, or towards the middle of the back, all are comfortable and allow quick access to the tool, such a rig I'm sure would adapt quite well to a knife sheath for a knife that big, the materials are inexpensive and the rig is easy to make.