Hi everyone.
I'm still lurking here even if not actively working on anything FSO related now

I did not even know there was a discord about some SL port ^^
To provide a quick answer, I won't probably bother to convert any more things from SL (as I would need to learn again as my time as gone into D&D and excel programming!), but to convert these models here is a quick explanation about what I can recall without goint into too much details:
-first I extracted models from the SL cd-rom with an old utility allowing to view *.hog files contents (that tool should probably be available somewhere on the internet and my hdd lol), then exported them to ms3d files (milskhape 3d) thanks to a plugin
-then from ms3d I could export them to blender which is much more friendly for working and exporting a model to the FS engine (you will have to search by yourself the naming convention used in FS engine for your tree model). That would need resizing and moving objects to their correct position.
-from blender you can texture and edit your exported models (like adding turrets, weapons, subsystems, etc...) by following the correct naming
-then export the model to dae using blender build-in export tool ans import the resulting file in POFCS2 to save it as pof file that can be used inside FSO engine (that will need tables too

)
-adding debris and the like is a bit more work that can still be done with blender
Edit: attached a zip file with a word doc containing my personnal notes about converting these models and using blender (I was learning at the same time so bear with it ^^) some text is probably in mixed french/english (as I'm a french guy!)
[attachment eaten by a Shivan]