Alright, I'm sitting here with Doug's knife and the Bianchi sheath.

With the clip in place, there is no noticable gap on any of the sides of the knife, though I suppose it would be a little loose if the clip were removed.

To test this I placed the knife w/ clip inside the sheath in all four possible orientations and turned the sheath upside down, each time holding the flap back out of the way (so it wasn't holding the knife in). The knife never fell out, though in all orientations, a few shakes of varying degrees would certainly result in the knife falling out. Hinge down/clip toward snap was the loosest and would fall out with a simple shake. My preferred orientation is with the hinge up/clip toward the belt loop, and took a few mild shakes to fall out. My point is that the knife is fairly snug in the sheath pocket. Of course I have no plans to carry the sheath upside down with the flap open.

Using the second snap - the one that produces the smallest gap between the top of the knife and the top of the sheath - there is indeed a gap. But I measure that gap to be only 1/8" to 3/16". Is that even enough to worry about? Yes the knife will move inside the sheath top to bottom when shaken up and down, but I'm not planning to do jumping jacks while wearing it. Considering the sheath isn't custom-made for Doug's knife, I think it fits pretty well.

My biggest concern with the sheath was the propensity of the sheath's snap to accidently come unfastened while being brushed with my arm or a pack. It seemed to me that a strong velcro fastener might be more "brush-proff". Time will tell.

If interested, here is how I measured the gap: With the knife inserted with the hinge end toward the folded top, I placed a piece of tape on the side of the knife exactly where it lined up with the top edge of the knife pocket and then pushed the knife as far as it would go toward the fold until it stoped. I then measured the distance (shift) from the pocket top to the edge of the tape. I repeated this with the hinge end down (inside the pocket), and the shift was 3/16" - that's 1/6" more.