Garf did some studies on escape size and growth in SPS and discovered (this has been years ago now) that when they were mounted at about an 8:00 position, they encrusted and put out more branches quicker than a vertically mounted frag (and much faster than the mother colony, which is where escape size comes in). I mount mine vertically or off of vertical (sometimes as much as 45-60 degrees), but that is just a preference thing for me.