Before I head to the office I pull a couple of singles for taste, crema and to open my eyes. Then I pull an Americano with a double pull on the Pavoni, and then add equal parts of water for a 1:1 ratio. Why 1:1? It is the size of the cup I use, so it works for me. BTW.... my commute consists of walking to the spare bedroom and booting the computer.
Hmmm, I have never tried to preserve the crema in my Americano.... something to try.
On another note, I recently ordered an Americano at a shop in Columbus OH and the barista actually asked me what ratio would I prefer? I was impressed.