Jackaroo747
For that kind of extreme low flying you are not relying on ANY instruments - it’s purely an eyeball exercise. You just fly as low as you can without hitting the ground. Flying in a straight line is pretty straightforward - it’s the turns that cause the problems. You have to climb a little bit every time the bank goes on to avoid digging in the wingtip.
In my experience the HUD just gets in the way of a clear view forward, even in a single-seater. A good Head –Down compass display (Like we had in the Hunter FR10), just below sightline is fine for heading-keeping. I was never very impressed with the Tornado’s double combining-glass HUD, which made forward view even more difficult when it got a bit dusty.