Fair-enough question, Rivett. No, we do not carry two performance manuals. FO Bloggs works out the numbers from the book and writes them on the Takeoff Data card. He then closes the book and chucks it on the coaming. When I'm ready, I open it at the page I reckon we should be using (eg packs off, wet, correct intersection) then with the card, find the flex temp we need. Then I start checking his work.