I'll update here if I find a way we can tweak this. The rss feed does truncate the post (as in the old forum) but it would be nice to have a few more lines.
One alternative if you want to get the entire body of the post - turn on a watch for the Category, Forum, Thread or user you want to follow. Watch emails include the username of the author, the forum posted in, the time stamp and the full text of the post. It's a different way to receive the content but it gives you much more info.