How many Super Isol boards?

[Ted Rosenberg]

I am getting ready to build a 42" Pompei. How many 24" X 30" sheets of this material should I get? What is the best way to cut them?

[jwnorris]

I am building a Casa 110 [43" I.D.] and purchased four sheets - three is just not enough to cover the entire base.

J W