Well, I discovered by accident, and have looked through the documentation to see if there is an explanation, but have not found it. At any rate, I too discovered it was difficult to create unwrapped models that looked correct. Here is what I found.
I first grab the left side of my aircraft model and map it to the TCE.
This view has not been properly flattened so I can create a 2d texture. So, I then map it using LSCM. Here is how it was mapped:
This is of course stretched out of proportion and I would typically mess with it and move vertices until it looked better, but it still was not mapped very well.
So, I hit CTRL+Z to UNDO the mapping. But to my surprise, something else happened. This image appeared:
I thought, WOW, this is much better! So I flipped it both horizontally and vertically and also rotated it a few degrees and now have a properly flattened 2d ready for texture creation.
Don't know if this function has been there all along, but I sure like how it flattens my models now. They now appear very symetrical, as they should be.