Your other option is to use a current animation and scaling it.

To to this you need to unpack the skeletons. I believe Lotr's trolls use one handed weapons.

Once you unpack the animations you'll see a bunch of new files in the animations folder (all have fs_something written). Use extract_skeletons for this [its a bat file that comes with xidx].

Take, say, fs_swordsman and make a copy. Call that copy fs_troll.
There should be a list.txt. Enter fs_troll in that list and save.

Now, you need xidx for this (sorry, its been a while since i fiddled with this). Best thing to do is run the xidx.bat (place it in the animations folder) type HELP to get a list of commands. You will need to then type scale fs_troll.

then it will say something like scale fs_troll 1.0

type scale fs_troll and then enter a new skeleton size. 1.3-1.5 should do it.

it will then say something like new scale is.... whatever you made it.

Now all you need to do is pack your skeletons and this part is done.

Now in descr_model_battle go to your troll. In the skeleton section type fs_troll.
Example:
type mordor_olog
skeleton fs_troll
indiv_range 40

The game now knows which skeleton to look for. Run the game to see if it works. Should your model look a bit awkward then add

scale [followed by # of the size of the new skeleton]
Add that under skeleton

Example
type bree_hobbit_peasant
skeleton fs_hobbit_spearman
scale 0.7
indiv_range 40