I am trying to develop a prototype tool for polishing and ideally want a polyurethane mould that is around 40shore hardness.  I purchased some Xencast P30 & P60 to experiment with.  The 30Shore is definitely a little too soft and the P60 is too hard.  Is is possible to mix the 2 in equal measures (by weight) to get a hardness of around 45shore?  If it is possible please advise the procedure if not equal measures.  Thanks for you help.