Digital BW, The Print

I'm plan on to buying some MIS VM ink for my Epson 1280 soon.  I 
understand that Paul Roarke developed his curves using Epson Archival 
Matte.

I still have a couple of boxes of Epson Matte Heavyweight.  Are the 
two papers comparable as far as how they respond to the MIS VM ink?  
Will I lose anything (or have to tweak my curves) to use up my Matte 
Heavyweight?  What exactly is the difference between the two papers?

--Peter