Bridging on hollow cube

Right then, I've been experimenting with bridging on my Mendel90. I've successfully printed a the bridge touture test (http://www.thingiverse.com/thing:12925), but the hollow cube (http://www.thingiverse.com/thing:30171) is causing problems. It appears to be a problem with Slic3r, as the image shows the paths for the bridge layer do not make sense. It is starting paths in mid air I've played with all kinds of settings, and I manage to make it have sensible paths by increasing the number of perimeters. However, this made the infill really thick, so when it printed the infill was printed like a normal layer (bridging settings did not seem to apply).

Has anyone successfully printed this thing? or perhaps have an insight into the settings that may affect these paths?

Seems like Detect Bridging Perimeters is the only possible direct setting for this. Or change to a different type of infill.

I have "Detect Bridging Perimeters" selected, and the infill is set to concentric for both top/bottom and normal fill. Which is strange, as the zig-zags don't look very concentric to me!