I fitted a 265 Getrag with Mark Turnbull's bracket first, and I then fitted the original plate back. I have seen a great difference in shell rigidity as the hard top was doing all kind of noises on degraded surfaces, but not anymore. My suspension has stiffer springs so the issue must have somehow been magnified, but fitting that plate back really made a huge difference.
On my car the transmission is about 2 inches forward compared to the normal set-up as the M117 V8 is shorter. As a result the Gertag 265 clears the plate, which I think is not the case with the normal set-up.
I'm not sure the system shown in the pictures, with the spacers and then with an additional stripe of metal on the side, will ensure the same rigidity as with the original set-up. Reason being is that most of of the strength between two parts bolted up together is thanks to the pressure around the bolt. With spacers that surface is way smaller which may allow for some flexing. I would have rather designed an aluminum spacer with the same footprint as the original plate. Even though, rigidity is mainly obtained by the cross designed by the four angles of the plates. Having that cross lower may also introduce some room for more flexing.
In any case, the best solution, whatever it is, will most seemingly be the a compromise.