Source Control access to stream in parent team area in RTC

In RTC 4.0.7 we have the following team structure

• project area A
  • big team
    • sub team 1
    • sub team 2

We also have a stream that where the owner is big team. Some team members are only in one of the sub teams (not in big team) but should be allowed to deliver files and access files into that stream.

RTC prevents delivering a file when a member of sub team 1 tries to add a file into the stream where big team is the owner.

How can I allow the team member to deliver the files?