How to force a line/edge while using rotoscope

[Scout myname]

The yellow line I have drawn on my picture shows where the persons arm finishes and the person behind is becoming visible. I have been unable to use the Refine EEdge or Roto Brush tool to fing this edge.

If I try to select any part of the area close to the edge of the arm (where I have marked it with the yellow line) The rotoscope with selects a much larger portion of the front persons jacket in the front.

Is there a way to overcome this problem?

[Mylenium]

Start by pre-composing the Rotobrush stuff with extra room left and then refine it in the parent comp using conventional masks. Rotobrush simply isn't always the best tool for everything.

Mylenium

[Scout myname]

While this workaround does work, I am not sure if I should be saying 'correct answer' I am new to this forum and I am unsure what the protocol is

[ShiveringCactus]

I think it's safe to check "correct answer" here, if Mylenium's workaround works, then that's solved your problem and more importantly the next person struggling with this type of shot gets to see an answer they know works.