after reading this thread and lamenting my own mash inefficiencies, I decided to up my ratio yesterday. it made no effect.
15.5 pounds of grain, beersmith recommended 19.38 quarts of water. I always round up to the nearest gallon anyway (five), but I figured I'd bump it up to a full 24 quarts. still stuck at 60%. granted, that's still only ~1.5 qt/pound. maybe today I'll get it closer to 1.75 qt/pound and see if that helps?
edit: my mash temp was a spot on 150 deg and 5.3 pH at the start, I stirred several times throughout, and ended up at 148 by the end of the sixty minute mash. I sparged with 185 degree water and noticed the sparge was only 165, so maybe that was part of my problem? initial runoff was 1.060m OG after boil was 1.066.