Crush it 'til you're scared. You need to get the starch outta the husks -- conventional wisdom holds that crushing the hell outta the grain is the way to go! As long as your sparge flows and you don't taste tannins, crush away. I absolutely pulverize my grain and brew award winning beer (blue ribbon at the Los Angeles County Fair this year with an Imperial Red). 75% eff is nice. 89% is nicer still. My 0.02.
"Good people drink good beer." -HST