Eh, this should be no big deal. The passenger cabin shouldn't be doing any crumpling so you're fairly free to throw metal at the problem. All the mods are in

Eh, this should be no big deal. The passenger cabin shouldn't be doing any crumpling so you're fairly free to throw metal at the problem. All the mods are in the rear and there's no airbags for rear impacts (most of the job of crumple zones is to buy time for the car to detect it's actually crashing and deploy airbags) so any difference is gonna be minimal. Maybe the roof structure is compromised but once again that should never crumple so you're free to throw metal at the problem. Obviously there's more details to it than that and there's more and less elegant ways to "throw metal at the problem" but that's more or less what real automotive engineers do when a cabin design needs beefing up. Sure the lack of complex simulation software for this build might have left it with some Achilles heel but plenty of cars leave the factory that way too.