I was under the impression that the relaxed location rule had hit the GCR. I think that the area from the passenger seat footwell to the area under the seat will be the approved location.
Regarding the cage locations, while the cage may actually bear on 8 points, (and two don't count,!) if the car was inverted, the weight isn't going to be dispersed equally among the 6 remaining....or even the 4 main points, AND the weight will be significanly more than 200 or so pounds!
Honestly, I'm not an engineer either, but I do have some common sense, and this weight excuse is a huge red herring. There are dozens of ways to mount the weight. Can you define the term "Backing washer"? Do you think a tech official will not approve your car if it's too large? Not round? Welded to the floor and into some surrounding reinforced area?
Is a competitor going to protest it if the structure you fab to mount the weight to is stout?
Obviously, lets not start welding U channels like I have seen on some Rx-7s running the length of the floor, (for "jacking convenience"), but a reasonable reinforcement is appropriate.