Haha, thanks for the welcoming post mate. I've included a few pics of the City below, along with some of my creativity with a ZX9R exhaust :)
I'm definitely considering making an investment in a custom expansion chamber. The only concern is the cost, as either option will cost more than $500 to land at my door. Example pics attached. The improvement is undeniable though, with around a 10km/h improved top speed, making it able to hit almost 30mph!!
I'm still weighing up engine options, but on the back of the help I received here yesterday, am thinking of using a Puch head with all the extra cooling area, but re-drilled to suit the Honda pattern. I'm thinking of going with the Polini or Malossi 70cc kit, since they are more plug and play than the Athena (plus a 46mm Puch head is easier to find than a 47mm one).
Anyway, some pics below.