I've installed the 5.026 beta. It did not ask me to convert the 4.something database, but when I copied the database over it did it fine.
However, the 5 beta has no filters. So I guess I need to copy the filters over too. Except that I can't find them. Which file has them? (And I hope there will be a new beta very quickly that after deleting a file selects the next. That is one annoying bug!) Oh, now that I'm writing this I note that my signature has gone AWOL too. What file has that one? V.