I guess I miscommunicated my use of a Phonebook.
I always use only 1 heavy technical maunal or phonebook between the Jack and the Car's center frame member. I do this for safety. The heavy book molds, or conforms, itself to the Jack Saddle and the Center frame member and gives about 3" of additional lift.
Instead of metal agianst metal which can be slippery,(because of oil, grease, etc.) the semi-pliable phone book/tech manual actually kind of "glues" or mates the two uneven surfaces together as it it gets crushed slightly, and spreads the weight around a little bit. Its true the phonebook gets chewed up and you can only use it 5 or 6 times, but thats why I raid the recycle bin. The book also protects the metal surfaces. Without the book, you would be surprised at times just how liitle contact there is between the usually dish shaped saddle and curved center frame member. Furthermore, it protects the oil pan.

Now of course maybe I am wrong and just lucky. I'm sure there are countless ways to do this; whatever works safely for you is the Best way. Whatever you are comfortable doing is the best way for you...