I make the models in a program (Demo

called Imagine(kinda like 3ds, but crappier), including the mapping.
I wrote a conversion program to change the Imagine Objects to LODC, creating what I call the "parts" file. I never edit the parts file, what I do is reference the "parts" file from another file, in such manner:
"airplane.lds"
---------------
split
include airplane.parts wing-right
splitb
include airplane.parts fuselage
splitend
---------------
"airplane.parts"
---------------
group wing-right
POLYGON...
...
groupend
group fuselage
POLYGON...
...
groupend
----------------
This has a great benefit, the splits, switches and other LOD specific stuff is in the LDS file, which makes it managable.
, and the physical stuff (points/polys etc) are in the "parts" file. I can go back to Imagine, make changes to the original object, convert it, and recompile it without loosing the split structure.