In NSW if attending an event hosted by a club other than your primary or secondary listed clubs they must also be a member of the CMC or be a special event sactioned by the CMC.
You can take your car on any event listed on the CMC calendar as it is an invite for attendees of affiliated clubs, if you notify your historic plates rep.

Reminder for those on club plates in NSW be careful not to have your car photographed on ausmini runs as ausmini is not an affiliated member of the CMC and your car is unregistered and uninsured if you do. There are members of the CMC who look at this forum and notice.

I guess that is the reason why I built another mini and the Cooper S sits in the garage for 362 days of the year

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1969 Cooper "S"
1967 Mini Deluxe
1973 Clubman Van (the fleet spare)
1978 ex 1275 LS ("Wizard" Eaton Supercharged)
2015 HSV GenF GTS(occasional drive & tow car)
2019 MINI F55 Cooper S

"...and your car is unregistered and uninsured if you do."

Unless your club adds the run to their events calendar...surely any club run for the benefit of members would not have a problem doing this...

Cheers, Ian