For anyone with original Jota handlebars, any more than a couple of mm is not possible. But since you have clip-ons, you can shove 'em through as much as you like. For road use I find the normal setting perfectly OK (no protrusion above the top clamp). For track use, you might want to sharpen up the steering a bit. Give it 10mm and see what happens. If you can't feel any difference, give it a bit more. Be careful with lean angles though. As you drop the clamps down the forks, you also reduce your ground clearance.