buggsmasher,
Not an easy question to address and certainly one wherein generalisation may be more distracting than illuminating. While the present thread has, as its interest, fin loads, the following more general comments may be of some use ...
The Type Certificate Data Sheets will give an indication of the design standards which were applicable to a particular type. A review of the relevant issue (and the host of anciliary documentation) will give you an overview of the certification requirements applicable at the time ... Then there is the issue of design variations, concessions, equivalent safety determinations and the like .. Upshot is that, unless one is with the design organisation it is near impossible to find out just what was or wasn't done, especially in respect of matters extending beyond the minimum requirements. To a large extent the Industry relies on the professional integrity of the design organisation and the assessing regulatory body to give us some measure of protection .. and we have seen a few major screwups over the years where such reliance was proved to have been misplaced in the hard light of inservice experience.
It is important to realise that the people within the design and certification areas are just as human and fallible as everyone else. I have seen very competent engineers make assumptions which are quite reasonable to an engineer but which are materially at variance with what happens in the real world environment. Further, with modern design of large aircraft, as the projects become larger and discipline specialisations increasingly focussed .. there is the problem of overall design project management and what might slip through the cracks ....
To me the principal guiding light ought to be for the operator (and the operator's pilots) to follow the guidance which is laid down by the manufacturer (and ought to be in the operator's prescriptive documentation) .. for the simple reason that such guidance is based on the (usually unidentified) assumptions made in the design and certification processes. It really comes down to a matter of trying to walk through a minefield with marked safety pathways .. certainly you can step off the marked path and not have a problem ... or, conversely, do so and have a big problem ... difficulty is that you have no way of knowing outcome probabilities in the absence of data. It all comes down to a matter of sensible risk management and risk minimisation practices.
While being of sufficient modesty not to reproduce his comment here ... the earlier observation made by HOMER SIMPSONS LOVECHILD does, I think, sum up my thoughts precisely ....
My own worries tend to look less toward static strength problems (although the failure characteristics of composites can present some excitement) and more to the fatigue consequences of operation and maintenance practices which are at variance with the assumptions made within the original design and on-going MRB systems .. and we have seen a number of fatals over the years due to precisely this consideration. Having been involved in earlier lives as an engineer at both ends of the process I can only urge a conservative operation of the inservice article ... there are just too many imponderables and, as airframe lives are pushed out way beyond original life cycle projections, too many opportunities for spectacular outcomes.
In respect of your monsoonal observations, this is an example of the sort of situations which give rise to longer term cumulative structural concerns.
Scanning through the IFALPA/Boeing article in the link above suggests to me that Boeing, also, echoes HOMER SIMPSONS LOVECHILD's sentiments .....
This answer is probably not at all what you wanted ..... sorry about that... but, then again, if you have a TP background .. you know all too well all of what I have said above ...