I was concerned about the ability of this strap to stay in place even before I received it, visually it doesn't look like it would be very secure. But the grip (no pun intended) is actually pretty solid considering there's no locking or serrations. It lies flat, but I'd recommend not going a size larger than you absolutely need because when tightening it can be difficult to slide the tip of the strap under the overlap if you have too much left over. if it makes sense And yes, it does lie flat, but I don't think the protruding buckle has been an issue for me on other harnesses, so I can't comment on that.