I like the sheath so far but all I've done is inspect it visually and slid the Dogfather in and out a few times!  It does have a plastic insert. The fit is snug against the spine with just a hint of rattle on the edge side.  The velcro strap keeps it snug. The next few weeks will tell how tuff the sheath will be.  
The knife is a bit lighter than I expected (compared to my FBM) which is a plus for me because I will be using it in the field extensively for awhile.
So the big question is how well does the FBM fit in the Dog Father sheath?