A few inches below the knee seems a little low to me. I agree that you don't want them up at the crease behind your knee, but just above the swell of the calf kind of gives that look like your socks aren't really long enough to pull them all the way up. I'd aim for just below the bump on the fibula.

As far as flashes go, they are the decoration on a functional piece. You don't want to be forever pulling up your socks, and they do tend to creep down as you walk around unless you've got an elastic garter under the cuff at the top. This is _particularly_ true if you're wearing a sgian dubh, which can submarine a pair of kilt hose _really_ fast.

Barb