I'm not sure if I mentioned this at the time, but I also recently refactored the large message reference counting code, and paging manager addsize code.
Now, all calls to addSize are done in one place - this makes the code a lot simpler and easier to understand.
Also, large messages were hijacking the ref counting to handle large message file deletions. This played havoc with page sizes in memory and it wan't a good separation of concerns, so I removed this and now large message manages its own counter which is specifically used for deleting large messages.
