Lew,
Would stiffness really be such a consideration with any of the materials we are discussing in the situation that it will be in? Don`t get me wrong, it needs to be stiff but would the period really vary due to this factor whether aluminium, steel or plastic was used?
I do understand most of what you have written but I`m curious why such a prolific clock builder, John Wilding, would have suggested Paxolin as the most suitable material if it was not the case - aluminium, brass and steel are used elsewhere in the clock build so he clearly could have choosen this during the build - yet he specifies Paxolin.
Regards
Chris