More straightforward when we had the Australian specific DoT AFMs but they've been discarded and the requirements of CAO 20.7.4 re soft dry grass and runway slopes don't fit with an older typical FAR 23 AFM or POH and the weasel words in the CAO are not enough to hang your hat on.
Nil authority to continue to use those old P charts, if you do then you are personally responsible - I asked CASA to provide the test data and analysis for the 8KCAB Decathlon and got nowhere. I suspected that some bright person had provided an 8KCAB with 180 hp and C/S prop for the performance testing - where did that leave me with an 8KCAB fitted with the standard 150 hp and FP prop? The P chart is simply labelled 8KCAB. Manufacturers info? - that's another story.