Must admit, I had a difficult time following funstuff's post.....Below is how I determine the distance to play a putt.
If the putt is "X" inches "up" then add "X " feet to the distance to determine a calculated distance for the putt; if the putt is "X" inches down then subtract "X" feet to determine a calculated distance.
If the putt is on "fast" greens, the calculated distance is the distance to putt.. If the putt is on "slow" greens then add 20% to the calculated distance. If the putt is on "very fast" greens then multiply the calculated distance by 85%.
As an example....let's say one has a 15 foot putt with 5 inches up; thus the calculated distance is 20 feet.
If on fast greens, one would play the putt as a 20 footer.
If on slow greens, one should play the putt as a 24 footer ( 20 feet + 4 feet [ 20% of 20 =4] ).
If on very fast greens, one shoud play the putt as a 17 footer ( 85% of 20 = 17 ).
Harve