AS you pointed out in your Field Guide of this level you can march your units off the edge of the mesh. It is curious to note that once you have done this the units must completely dissapear, as you cannot even view them on the toolbar with presets.
It is also interesting that despite the 'Myth Player Guide' said you simply cannot defeat the entire force you are trying to lead across the bridge a friend of mine and I did so.
The film in which I discovered both these wonders is availavble if you want to email me :).
Keep up this GREAT UNBELEIVABLY FANTASTIC site.
