I don't know if this link will work however there's a guy posting his story and pictures over on OCOA about making his own version, very much an original, offroad trike. So far he's machined his own hub, chainring, working on the spider and so on. And not using 20" tyres, no he wants something that'll crawl up anything regardless of the weight of his wheels. And power-assist.
http://forums.overclockers.com.au/showt ... 606&page=1
If this doesn't work then perhaps he might be persuaded to post something here. There was also an earlier thread from another trike builder on OCOA.