I finally got around to adding liners to my GSO-10, took me a while because I couldn't find those trimmable car mats close by and low enough cost, ended up tracing/cutting liners from an old wheelbarrow inner tube. What a difference!!! I'll post pictures either this evening or tomorrow when i have a chance to take some photographs.
By the way, the tricky part was remolding the sheath-mouth to provide proper retention on the thicker handle - you have to heat it up to loosen, then repress tight but with a spacer around the blade and a flare at the lip so the knife still goes in easy. Thanks to FTR-14c for the inspiration!