Mafero:
Give it a try. If however you are trying to increase the girth of the proximal end of your penis, I think you would do better withthe larger tube ( I have the ame dimensions as you, and I have a 1.75 for length, and a 2.25 for girth which works very well. There is no doubt that you will get more length with the narrower tube and more girth with the wider tube).
Edema will be less of problem when the entire shaft is exposed to the same negative pressure,but will still occur if in the tube for any prolonged length of time, e.g. 30 minutes and 10 inches Hg..