Since you are becoming an engineer.. I think this would make good discussion..
http://en.wikibooks.org/wiki/Nissan_..._Strengthening
Extract from Mr WIKI...
C-Pillar Bars
The s13 hatch in particular has a fair amount of flex in the C pillar area due to the extensive size of the rear opening. A viable upgrade would be a C pillar reinforcement bar that bolts to the rear seatbelt mounts. It should be noted that the mounts on the s13 zenki ('89-'90) are more towards the glass and the s13 chuki ('91-'94) hatchback seatbelt mounts are parallel. A solid metal bar may be economically produced by measuring the distance between the 2 points and drilling mounting holes for this model.
Note: These bracings are produced as well for coupes but in those instances tend to mainly just be cosmetic since its not a weak point for them.