Thinking about this further, I remember the discussion...
Thread 'Just found the upper limit'
https://berean-apologetics.community.forum/threads/just-found-the-upper-limit.1390/
I'd written a really lengthy post.
I'd gotten to the point where I remember thinking - this is going to be a problem.
I posted, saw the error and then noted the message limits... 21,700 characters...
It surprised me, but I was pleasantly surprised.
This generally resolved my concern, because I seldom reach so many characters.
So, I think I'm good with this one now...