Convert stringList to text property ?

[Daniel]

I've got a running app running that serves my game.  I store chat messages as db.StringListProperty which in hindsight was a bad idea.  I get this error every so often:

Property chatLog is 532 bytes long; it must be 500 or less. Consider Text instead, which can store strings of any length.

So I've got thousands of records with chat logs in the StringListProperty.. I'm assuming I can't simply change it to a TextProperty and things will just work.. so what's the right procedure?  Do I make a new Text property to store the chat and copy the data across?  I like having things in a python list but I suppose I can use json to serialize a list and shove it into a text property to retain that behavior.. 

Thoughts?  Is that the right way to go?

Thanks