i have the wild things [nylon] windshirt and wear it a lot. (ALWAYS take it climbing outside.) if i'd had more money at the time i would have gotten the epic one. some day ...
i don't think they were recommending paying out 20 feet of slack at all times; just some numbers for examples' sakes. (i hope!!!) and you can NEVER have a fall factor over 2.
rope stretch and other components of the entire system will also play a role in the fall factor, but yes - i believe that's why we're taught to belay leaders with some "slack" payed out ...
geez, dr. that's some project!
i'm thinking denali myself. but maybe that's a 2004 project. something closer to home - maybe the grand wall. just for fun. and i'd really like to do some climbing in yosemite.