2009-11-13: I'm trying this today because I want to see if I can loan out my stock that we're holding long term.
It takes a couple of days setting up. I've upgraded my account to Portfolio Margin, which is meant to lower the margin required by considering related positions.
Next task I had to do is request trading access separately.
2009-11-17: After getting trading access, it seems I cannot loan out my stock. The shares must be held by DTC, but my shares are held by IB.