No, Mobius, this is not derailing.
You see, in the end, it's like this. 50k characters is enough. As has been pointed out, that's equivalent to about 9000 words, or nearly 40 pages of printed fiction. Now, I can't fault you for having the creativity and perseverance necessary to write that much, but at some point you have to ask yourself if you really need that much, or if your intended audience can actually take that much.
For reference, the entire Blue Planet ref bible, which is our repository containing the entire backstory of BP, dossiers of most of the major players in the BP universe and other stuff, is currently at a little bit under 50k characters, and even that is too long to be considered postable.
Now, regarding storage, several things have been pointed out already that could work for you even better than forum posts, like files on a shared FTP server, or files stored in a version control repository. If you need help setting up the latter, I can help you out. Since you are looking to distribute these bits of story so that your team members can look them over and submit corrections, a version controlled storage site, like Launchpad, github, or Google Code would be best for you.