What you have to remember is that Lithunwrap v1.3 is a FREE UVmapping proggy ( and v1.3 was the last FREE version made )
Now it is NOT free ... and the name has now changes to "Unwrap3D" which is currently on version 2.03.
It also has a hell of a lot of new features and BUG fixes from when it was "Lithunwrap"
Basically if you are still using Lith ... which is still a good UVmapper, then you have to put up with some of it's quirks. ( exporting to .X being one of them )
One way to keep your model smoothed is to save it out in the same format it went in ...... then load the model into the modeling program from which it was created, and export it out to .X from that.
If you are using a modeling program which doesn't export to .X ,,,, then get one that does !
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