I have an application that I'm going to publish to the Android market. I'm planning on releasing a paid-for version and a free version with restricted feature set.

During development I've ensured I can turn features on and off by setting a few constant values, so I only have one codebase.

However, now I come to release I'm not clear if I need to make a copy of the app with a different package name for the free version.

The documentation on how the market works say updates will only be recognised if they have the same package name and are signed with the same key. Does this mean it's OK to release two applications with the same package name but signed with different keys, or will this break something? Or is it just bad practice?