The problem was, I guess, that the previous desert combat armor has size of 32x27 and this new one has 32x21, since there is no helmet with it, thus the bad vertical positioning.
The default fofrm file for combat armor without helmet is:
/data/faction.zip/art/items/caground.fofrm
fps=0
count=1
offs_x=0
offs_y=5
[dir_0]
frm_0=caground.png
I guess this just needs to be copied, changed to "cmbt_armor_desert_ground.png" and used:
/data/reloaded004.zip/art/items/cmbt_armor_desert_ground.fofrm
fps=0
count=1
offs_x=0
offs_y=5
[dir_0]
frm_0=cmbt_armor_desert_ground.png
Ty, SEGA, Arbeit macht frei!