From the
J/29 website rudder specs listed at the bottom of the page are "Temporarily suspended pending validation of Plan A". That's been like that for a couple of years.
Comparing that table with the
J/30 rudder profile in the
J/30 Class rules indicates they are the same. I didn't see the J/29 rudder drawing so can't tell if the overall height and mounting locations are the same.
From a minimum weight spec, the J/29 is 25kg (55 lbs) while the J/30 minimum is 60 lbs.
So - it looks close, but I would measure to validate.