scavenge some junkers and turn them into something great:

http://www.atomiczombie.com/ the loderunner trike looks great for the heavy rider; useful too.

if you can't weld a local shop can do it for you. a bit of work but still real cheap and custom made for you.

the biggest thing for the heavy cyclist is strong wheels, BTW. most frames can handle a load far greater than their lawyer-inspired rating.