My mash is the typical 1.25qt:1lb ratio with a 1 hr mash and 15 minute sparge. However after the sparge, while the wort is being brought up to a boil I continue to collect EVERY. LAST DROP. of wort possible from the mash tun. This involves tilting the tun up on an angle and letting the grain settle, collect some wort, settle, collect some wort, over and over until almost reaching a full boil. A lot of work goes into growing, malting and milling the grain, so I believe in getting every possible molecule of maltose out of that grain! Its a little extra work that (I tell myself) improves the beer.
Your efficiency might also improve from using a higher liquor:grist ratio. If you use 6 gallons of strike to 23lb grist, your hitting a ratio of 1.04:1. I always use 1.25:1 for my beers, and usually hit the 75-80% mark. Although I have never tried with 23lb of grain before, so I might be in the same boat when I brew this beer!