sparkyy0007 over at talk polywell did a basic FE analysis of the reactor box, assuming 1/8th inch steel plate and 1bar internal pressure. http://www.talk-polywell.org/bb/viewtopic.php?t=3200&postdays=0&postorder=asc&start=1200 But the attached picuture is a nice illustration of why engineers don't build square pressure vessels, and why Rossi should listen to others.
Note that the stress peak is over 80,000 - ie not safe for mild steel that is probably OK to about half of that. Keep in mind that during the Sept test the temp got as high as 133.5° - equivalent to 2bar of guage pressure if it was saturated steam, also bending stresses are proportional to 1/thickness³, so very sensitive to the plate thickness.
