Why? It's rated by the lawyers at 350# for the frame.....and that's likely about 2/3 of what the engineers would rate it for. The issue would be more likely to be a rear wheel rather than the frame. You aren't really going to be taking that recumbent in any conditions that would create THAT much stress, you know, it's a pavement ride, and being a recumbent, you aren't going to be bunny hopping curbs or taking jumps.
tom daniels here in Clyde's will hopefuly chime in here about his Sun and the rear wheel he had built for it. A Rhynolyte, if I remember correctly....