Russell,
My recommendation would be to go Twitter-style and do the old 1., 2, like when your message is too large for one Tweet. Have your entire post in a word editor (MS Word, Wordpad) and know where the best break is at the end of a paragraph where it doesn't exceed 10K characters.
In the first post write Post #1 at the top and then copy and paste the first chunk. At the bottom write continued in parentheses, or (continued).
Then before someone can reply, you quickly create a reply and write Post #2 at the top, and then copy and paste the remainder of your content. This way you won't have to shorten it and we won't have to change the max character limit. Use the "More Options" button and preview the first post to ensure it'll fit when you set up the first chunk. The rest should be a walk in the park if you follow the above. Let me know if you have any questions.
Thanks,
Mark