Golfspieler: I don't use the 90 foot scale myself so I can't comment on that one.
What do you use for a 16 ft putt? You could use 2 moves on the 30 ft scale, all of the 15 ft scale or 1 move on the 90. This is the gist of the putting by avatar move method. What makes it work for me is the 1 move on the 90 scale is about 1/2" on the meter whereas the 2 moves on the 30 scale is almost twice that-more time for the meter to jerk.
One thing I should point out and Bollux was the one that clued me to this. The deviation factor when using the higher scales for shorter putts is exaggerated. Be careful.