I was thinking through the process for turning the boat right side up and realised that the centreboard would drop down if not held in place in its trunk.
That would be highly inconvenient, not to mention dangerous!
I toyed with a cargo strap passed around the hull but that was clearly not going to work.
So I simply dry fitted the centreboard pendant bushing, pulled the pendant tight and put a big, fat knot in it.
Crude but effective. That will do the job.