how come you cant run an exo halo, maybe exo a-pilar protection, but an internal diagonal, and internal b-pillars... I helped put together a cage for a friend this way... all the strength of an internal, all the space of an external...
im 6'-4" and I was more than comfortable in the front seats of the finished caged XJ...
Personally - B-pillars that attach to a 1' cantalevered arm at the bottom of rockers are not what im intersted in... B-pillars, C-pillars - all should attach to a nicely re-enforced set of uni-body rails... at the rails...
A halo above the roof to keep head-room, and a internal bracing is the best way to go...
I dont run a cage yet 'cuse i dont have the time to make one right... and will drive like I dont have a cage untill I can afford the time to make one right...