This may or may not be helpful, but I'll add it.
My coach watched me clean and said I had enough flexibility that I should really try to keep close to a full grip on the bar into the rack position. I concentrated on doing so, and now I don't have a big open handed rack. I simply had to put my mind into it--I never thought to do it before.
If it is a flexibility issue in the rack, work on your thoracic extension mobility and wrist extension mobility.