If I were to build a recumbent bicycle, I'd consider building this design which can be fabricated from the steel frames of existing bicycles:
http://www.atomiczombie.com/!marauder.htm
The designer seems to be a whiz at creating bicycles and robots. He may be crazier than most of us, however, as he has already ridden his 12 foot tall bicycle - 12 foot seat height made it a Guiness world record - and has plans to ride a 24 foot tall one after he's completed it.