Thanks!
I got a 54T 130 crank set winging its way from china -- and I now already have a new rear 14t cog -- so I will just see what happens once I get the 54T on -- I can always put back the 18T that was there -- or just get some other size.
Likely this new setup will have a top gear (7) that will be too hard unless downhill or with strong wind to my back -- since it will be 54T front and 14t rear with my Nexus 7 internal hub.
The crank arms I ordered are 170mm and the tires (Dahon) are 20" x 1.75"
Thanks again -- I am much happier with the new 14T cog on the back! I'm no longer just effortlessly spinning gears all the time.