Foam Blank Densities

I’m planning on shaping a hp shortboard during this summer, and I’m trying to decide on which Marko blank to buy.  What I don’t really understand is the density number for blanks.  What density is normally used for eps/epoxy hp shortboards, and how does the density correlate the the strength and weight of the board itself?  I had searched but have not found any answers regarding surfboard blank density.