Digital BW, The Print

I've recently purchased a large quanity of Crane Museo Paper to 
print a series which is very graphic i.e. black blacks and white 
whites without much in between. However, the Museo (at least when 
set to Heavyweight Matte)prints very splotchy blacks when a large 
black area. I don't have this probloem with Ham PhotoRag or Orwell 
and I'm wondering if there is a way to rectify the problem.

Thanks for your collective wisdom.