I would try if only to know what's dragging down the fps the most. It could help finding other workarounds. Then balance to your taste.AI cars are already at medium. Anyway, pb between T5 and T6 occurs even when i'm alone in this part of the circuit.
I may try to put track detail at medium but usually, there is a big step between high and medium, my psychological step between acceptable and not acceptable. Same with shadows, when it's too low I feel I'm in GTR2
However, getting rid of some post-effects doesn't kill immersion so much and help fps
I don't know how good is rF2 at discarding objects which are out of sight when rendering. So maybe the issue isn't exactly what you're seeing, but what's behind or next to.