I would never use malloc/dynamic memory with less than 32k of available space. From my experience, that is suicide (death by frustration). To make method even have the smallest chance of success, you would need to add so much error checking and heap size checking that your flash usage would go up considerably to handle the additional code.
A couple of things to consider:
- Are you checking all return values in your allocation?
- If an allocation fails, what is your recovery or user notification?