Leather jackets appear to always have nylon or other synthetic lining, which should melt onto skin.
T-shirt cotton is not that flammable - thin cotton dresses may be, due to air surface contact.
I suspect, if no-one is in the RHS, any sideways impact to the right will jerk me out of the diagonal part of my restraint.
I once used a 4-point harness with a lot of sideways force, and my head smashed the glider canopy, (with no adverse affects on the head.)