I have a Zenith CH601XL with a Jabiru 3300 engine. Jabiru has posted a bulletin requiring the replacement of all through bolt nuts with ones that don't meet common aviation standards (threads extending past the nut) and then locking the nuts in such a way that the torque can not be double checked. There is some issue not to be addressed here that this is solving a possible non problem and in the process having a significant probability of doing harm.
This update does not have the word mandatory in the title it as a Lycoming "AD" level document might but the intent is there.
The question is, as an experimental aircraft with an engine which has been modified in other ways anyway, it is still a legal obligation to perform all manufacturer specified updates?