I wanted an Xtracycle, but didn't have the $450 to get started. I also don't have the ability to weld, though I recognize welding is awesome. Instead I built my own using rivets and square tubes. The square tubes make the riveting easier and allows the tubes to form their own jigs to maintain alignment.
I have more pictures of the build here.https://www.flickr.com/photos/willevans/sets/72157623031041775/

I have more pictures of the build here.https://www.flickr.com/photos/willevans/sets/72157623031041775/