Our native Highlanders generally recommend wearing it with the kilt somewhere between the middle of the kneecap and the top of the knee (with their preferences trending more towards the top of the knee).
Those who grew up wearing the kilt in Scotland are likely to agree. The concomitant issue is the height of the hose which may be incorrectly pulled up like football socks so that hose and kilt almost meet. You will see experienced native kilt wearers with the top of the hose three or three and a half inches below the centre of the knee cap. Knees are definitely to be seen!