Hey there, Fuller.
Now that you've mentioned what knife it's for, I gotta emphasize my suggestion even more about getting a stud that's pretty big. Knowing what I know now, I'd make my next one more oblong, like this:
It's because the blade is so wide, that especially when you allow the handle to cant forward or back, it forces the belt to twist a bit, which can allow a gap big enough for the stud to slip through. Sorry, I don't have a picture of what I'm trying to say here, but it's quite obvious once you've carried it that way for a while.
Also, there's been talk of the material for the scabbard itself. Leather, wood, kydex...
The safety thing is more important here because you want to carry it tucked through your belt. If you fall on it, it can't get away from your body or flop out of the way like it might on a belt loop. It's gonna twist until either your belt breaks (unlikely) or it splits/cuts the scabbard. Might get the end of the crossguard poked into your gut pretty good, too.

But aside from that, here's the simple reason I prefer wood. Think about what happens to the scabbard while you're moving around using the knife. Your belt will put quite a bit of strain on it, and would easily bend leather or kydex (perhaps even permanently creasing it?) so that you can't easily resheath the knife. A wooden scabbard that's still no thicker than the handle of the knife will take the strain much better in my estimation, though I admit never trying it with kydex. Haven't seen any thick enough that I think would take it. 'Course, if you do go with wood, you'll need a metal throat & tip to keep it from splitting, and it will probably end up costing more than the knife.
Just something more to ponder.