What you need to establish from the cockpit view is "fixing the bandit in your line of sight." That means that the bandit is stationary in your view through the canopy, along the line of your lift vector. If the bandit is moving up in your view, you're probably too fast and outside his turn radius. If he is moving down in your view, you are inside his turn radius, but it may only be temporary and you will overshoot and get into a scissors fight. So to establish a good lag pursuit, try to keep the bandit in one place from your view through the canopy.