You've tried reclining the seat just a tad and extending the steering column (telescope) to get situated?
In most cars that do have low roofs, seats are sort of always done this way it seems, as the Ferrari F355 I had the same issue, somewhat solved by doing that as well. The upright position is pretty much the preferred way in motorsports customs, but slightly reclined still, as long as all controls are still within operational reach and strength being ideal still, I've learned to cope in such cars like Formula Suzuki and Formula Atlantic.
I totally understand your issue though, as you have enough head room and there is no real aerodynamic or mechanical reason to be reclined aside from the head rest being designed for shorter folks with a different head shape...
I've bent my headrest posts on a old BMW the other way once, by taking it out and bending it carefully on a vice. That worked fine and put it where I wanted it, and I'm sure that would work fine on the FRS seats. Just be careful you don't bend the overall shape, and just kink it somewhere above the point of insertion, so bends do sit above the recess, so as not to interfere with alignment of the slots. Modern cars have very high tensile steel on occupant protection areas, and for this, you may just need to take it to a machine shop to do it safely and accurately, with the shafts being really stiff.
Better fitting seats are always safer than ill-fitting ones regardless of initial and universal safety concerns. As less worries and concerns, as well as comfort, are much safer on the road or track than anything that causes any of that.