Well, for starters, look at THSTONE's cage in this section, spec Boxster build. Make sure to include the "FIA bar" mentioned in that thread. If possible, post some pictures of Boxster cages the builder has done. Don't just let him do as he see's fit, get precise details in advance of every bar placement.
I am a big advocate of (what I think are called) NASCAR side bars. Two horizontal parallel bars with suitable vertices and bracing that curve outwards to the door skin from both the A pillar and B pillar. They work to ensure that, when hit from the side, the contact with the cage is as early as possible and as far from the driver as possible. Having witnessed the outcome of one Specbox T-boning another and destroying the outer bodywork without so much as a scratch to the receiving driver, I wouldn't drive on the track without them.
Linear Mode
