I think we could have everyone figure out what the equivalent to one computer text box is on their phones in the Admin thread before the game starts. I would almost suggest having post volume limits per, say, six hours, otherwise we'll have everyone saving their posts for the end of the Day and no one talking until like two hours before the deadline. But I think I'd agree with
G55 and say that capping the post length would be enough for one game. I'm biased, though, I'm one of the people who tends to post a lot.