Side impact protection is a challenge for any car.
There is no trunk/boot or hood length of crumpling zone to absorb the energy during a crash. There are 4 causes which can kill you in a crash,
1. Squeezed in the deformed structure -> try to stiffen the cage around passenger
2. Internal bleedings in your body -> too high G- forces on the human body -> try to use less stiff outer section on the car and gradually stiffen towards inside the car to reduce G-forces
3. External injury during colision of human with hard inside items in the car -> strap inplace and add softening Padding
4. Burning (fuel tank leak and easily flammable materials used)
A gt40 is not designed for any of these situations nor the replicas.
Next to this it is depending on how the side impact happens.
A tree, a SuV, a white minivan, a pickup, a hummer, a volvo, a caddilac...the weight and height of impact into the gt40 can not be predicted.
Body of the replicas made from polyesther will burn like a torch.
A rollcage will may help in certain situations but can make it worse in other situations.
Some people stiffen the side rails above the fuel tank but this can make it worse since those beams may intrude the cabin. Better to have the longitudinal beam above the tank limited linked with the inside cage so it can bend and absorb energy...
It is like the seatbelts, when driving an old cabrio, in some crashes it is better to fly out of the vehicle and you may survive, in other situations the seatbelt will keep you inside but you can headsdown first and kills you.
I agree with the "safety first" approach however you need to try to control what you can control...it is your speed, the operation of your brakes, the setup of the suspension,the condition of the tyres and your own driving skill, reaction, eyesight, the conditions (wet or moist roads...)
Personally I also looked to the chassis, I am restorating a gtd40 and it is in no way a safe chassis for hitting something.
Can it be improved ? For sure, a reinforced beam to support the roofbeam in the engine bay which may help a bit in a roll over. But what about the doors in that case...;-)
What always helps is adding aluminium honeycomb 10 cm/4 inch heigh panels to absorb energy in a gradually way. The question is where to add them... Preferable to the outside chassis rails but will not fit so outside of inner cabin rails..bit depending on which replica you have and how the cage is designed, material use and geometry.
Someone jumping in a gt40 with 500 hp and not being a bit afraid is dangerous. Rollcages and helmets increases only the sense of safety...which is a false feeling and make things worse.
It is the same with what we have in Europe called winter tyres...reducing breaking distance in snow conditions...guess what, people tend to drive quicker with them in snow now and more accidents happen...
This forum is to help eachother with his dreamcar however in my view there should be room for humor even with a serious topic as this one.
When you jump in a Gt40, you need to be aware it bites you and can kill you.
This is also part of the trill and sensation.
See it like skydiving...it is beautifull and gives a trill but there is always a chance you will come in too hard...no guts...no glory. So jump out and buy that gt40 ;-)