I'm 57 kg so multiply stiffness from me to you by 0.57. Further you're on a bigger frame so likely for the same frame model mine is already likely stiffer.
So I concur with the "sweet spot" comments.
Right there with you DJ-shorter riders on smaller frame would want more vertical flex and stress less about torsional or drive line stiffness. My system6 is a massive 60cm frame. The triple butted frame of course was pretty large as well. I thought the system 6 would rider harsher than it did, but I was really surprised how much more forgiving it was than the smaller OD tube of the triple butted frame. The rear of the system 6 is Al as well. If given the opportunity I would love to rebirth the system six frame manufacturing its a great frame-naked clear coat with polished or ano rear ends mmmmmm.
It really just comes down to another consideration for the kind of rider you are.
Is the frame stiff/forgiving for the type or rider you are- and of course does the bike fit you properly!!