Using a projector with unity and Impress, top panel shadow remains

I'm currently using Precise Beta 2 on my laptop.

One of the tasks I do with that laptop is to give presentations using LibreOffice Impress and a projector or second screen.

I use the Presenter Console, so that notes and overview are shown on the laptop, with the projector as external display showing the slides to the audience.

Initially both screens featured the launcher at the left. Obviously I set this to autohide so it wouldn't distract the audience. Now (early April 2012) Unity allows me to set up to have the launcher on the laptop screen only, which is what I want.

However, the external display still shows the Unity top panel, and I would also like to suppress that on the external display.

When the presentation runs the panel is hidden behind the slides, but the shadow of the panel is still composited over the top of the slide images. This I certainly consider to be a bug not a feature.

Has anyone else experienced this problem? Has anyone found a work-around?

Where should I file a bug or wishlist report?

Neil