A few suggestions,

 I'd consider replacing vb with vxf.  That'll give you mids and smalls and a lower expense ratio.  I'd also suggest replacing gwx with scz or mdd for a lower expense ratio.

As for allocation, obviously that depends on your other assets.  VNQ makes alot of sense if you rent, or don't hold a significant portion of your wealth in your home.  On the other hand, if you own a big house and a couple of vacation condos, you’re already heavily invested in real-estate, and you probably don't need more exposure to that market.

 Hope that helps