I guess you looked at the prices and wanted to be frugal There's calculations in the Otherpower book or Hughs book that will get you in the park . I suggest you pop for both .They are good to have around and kind of Historical in scope also .
I remember the first book I got on this subject I is still around but I had to find another copy on Amazon as the pages are in bad shape .
Go for it it will be it's good to have experience at your finger tips.
