Have you tried lining your sheaths? Using very thin veg-tan glued to the exterior of the sheath, you'd have a liner covering the snap body that could gouge your knife, Also, check out Norwegian/Swedish/Finnish style backstitched sheaths. They have a unique and removable belt loop. Here's a link to the Scandinavian sheaths.
http://www.britishblades.com/forums/showthread.php?22249-Scandi-Sheaths-My-Way