I built an Xtracycle last summer in anticipation of Cleverchimp's re-release of the Stokemonkey. We were looking for something my partner could use to ferry our 3 y/o to preschool with on her way to work and she was not digging the San Francisco hills nor quite ready to put the 3 y/o on the back of either her Vespa or my Vectrix. Clevechimp sent me the kit last November and I bolted it right on. So far I am delighted with the whole thing. Photos available:
I'd be happy to answer any quesions people have, or lend a hand to anyone local wanting to build one for themselves.