They turned up today - I can't see any reason they won't be adequate. The M3 cap screw is in double shear through the original stud and doesn't look especially strong, but some quick mathing gives me shear strength of 120kg (based on 2x the minor diameter) so it should be fine.
I don't believe that they were made in NZ based on the price, but they look well enough made and I'll be back if they don't stand up to it.