ok, thanks for effort.
i find some orthopedical way to force work this feature
for simplicity i tested it on model of engine "mship_addgear02L.imd", it can be found in my models.
1. import imd into 3dmax
2. choose desired part A (in our case is just one part inside imd)
2. just do mirror (copy+ i did not tested) = part B
3. import imd A again
4. switch both part A, B into editable mesh
5. merge (attach button) B into A (1. click on part A, then via menu attach/attachlist select part B.)
- result must be 2 parts in one with name of A.
- This way part B inherit properties of part A. If need , then delete original part A.
6. Export as obj (as imd game crash)!
7. Make imd via imdeditor (still missing gbnd, gelp,...)
8. test displaying of model in game
and for blender,
i modify models with textures only (because i still was not capable learn, how add texture to clean model), all models finish via imdeditor = raw imd model ready for 3d smax, there are added GBND and GELP, then again imd editor to finish ref. points, textures, guns,...
little complicated, but i have no better (faster) way, when consider my knowledge about used programs.