So, about 1.2 MB per file on average. How many more files do you have to add? :)
Those files are going to be synced over to your iPhone, where they probably won't be of any use, but will most likely contribute to slow syncing and application startup. If you've only got the desktop and the iPhone, and assuming my contention about performance is correct, why not just put links to those files in your database? I occasionally have a database of about that same size (5-5.5 MB), but when I do it is because one of my devices hasn't synced recently, I've done some reorganization, and the transaction history can't be compressed. I don't know for sure whether the resulting slow performance is due to the size or the large number of files in the database or both, but it definitely performs much worse at that size than at half that size where my database normally is. Syncing between desktop copies of OmniFocus only, I would say 5 or 6 MB with a moderate number of actions is fine.