I'd be pretty happy with 1/8" clearance. I'd be happier with even less. When I had my 4.5-14x44 Conquest in medium Conetrols on my 7mm mag Sako 75 I had no more than 1/16" clearance and I thought that was about perfect. Since I sold that scope and now have a 3-9x40 (Conquest, of course) on it, I've got about 1/8" or maybe 3/16". I can live with that.