can you remove a changeset from a stream?

I am learning the scm support model. and decided to try one of the ugly scenarios I had before..

create a stream, and workspace, develop on the app, and deliver changes,  baselines along the way.
now it seems I have another user, but a different configuration of the app.   the two cannot be in the same stream..

duplicate the stream,  rename the eclipse project out of the way, create a workspace and load the sandbox..
rename the project in the workspace, deliver
rename the old project back (to match stream 1)

two eclipse projects, two workspaces, two streams..  all so good..

oops.. I delivered a changeset  too many for the second stream.. I can see it in the change history.. but when I go to
remove it, it really creates another change.. so both are documented in the stream..  I can't have that.. it exposes stuff to the second user

did I create the second stream wrong?