I will try.
As I mentioned, there are two avenues by which sensors could detect the forces I am talking about: one would be wing flex sensors during horizontal turns: these exist but requires wing disassembly to put x layout “metal tape sensors” (?) directly on the spars, with electricity running through the whole thing.
The other would be, I presume, a thin pressure sensitive “patch” on the back face of the propeller blades, with wire or cordless recorder, and a light beam hitting the pressure patch to record the location orientation of any pressure variation within 1% accuracy of maximum load, and this fast enough to locate within one foot of the disc the variation within one rotation.
I do not know if such a patch device exists or even can exist, at reasonable cost at least, but if anyone can enlighten me I would certainly be able to invest a serious amount to investigate this: It seems to me like it would be a cheaper alternative to stick a patch on a prop than disassembling a warbird’s wing...: It would also be closer to what I think is the source of the phenomenon.
All I could find online about prop pressure sensors concerned marine prop research, so any help to find a maker relevant to aircraft propellers sensors would be greatly appreciated. Finding a warbird for such a simple test would actually not be that difficult, given the mild nature of the test, and I even have a local flying museum where several fighters are part of the collection.