Nomad, cheers, the frame is all steel and I used a MIG welder.
jasonh, it does take off from a standstill with the 28t.
The 20" x 4 1/4" rear tyre has a rolling diameter of 550mm compared to about 650mm for a 26" bike.
This helps allow such a small rear sprocket.
The bike is a little slow from the standstill, I wouldn't try starting off at the base of a really steep hill but once rolling it's great, the engine isn't screeming while cruising. It still pulls up hills once its cruising.
Cheers,
Matt.