That's a rugged sheath for sure!
Duane knows thick knives, it's been some time since I made a fixed blade sheath for a knife with a guard like that and when I made them I also would make the opening of the sheath large like you did for two reasons, ease of getting the knife back into the sheath and also it doesn't push the belt loop backwards at the same time. As to the wedges, I would take the leather welts to my sander and sanded/blended them down further back to make it a more gradual transition.
My take on stitching, I wouldn't do two rows, contact cemented downe and solid stitch will be plenty.
I might have made the sheath not quite as thick, it looks like you doubled up on the back and front panels ? Possibly for heavy duty protection for the user? If the leather used is heavy enough, one layer should be fine.
The restraining strap, since the knife has a double guard, I would have put the strap on the other side, so that when the person is walking through the brush it has less chance of getting unsnapped by accident, as well as being out of the way when taking the knife out and returning the knife back, lessens the risk of getting that strap cut. Also in making the sheath I would make the lower third close enough from front to back so it squeezes the blade a little bit, adding some friction retention, not a lot, but it helps to keep the knife in the sheath a little better.
But pretty nice stitching there man, a LOT of work into that one! What size thread did you use for that? I just got some tiger thread 1.2 mm that I'm liking pretty well.
G2
here's a link to a short tutorial I did that had to have a pretty thick welt to accommodate the guard that was made for a friend, always be careful when you tell a friend you might help out one day...they tend to remember such things better than you