COW will crash out in modern versions of FS2_Open. It was built for a much older version and when we moved over to HTL for models it stopped working properly. Hopefully one day someone will fix it as it was kinda fun.
As for STL my bet is that you don't have the requisite files it need. Remember that it uses the FS1Port and Lightspeed's nebulae. You've already said you had the port but did you remember to set up the command line to take advantage of it? Your command line should have included something like this -mod ShroudingTheLight,FS1Port,mediavps
You'd also need to have the nebulae like I said earlier. There should be a download for them as a VP around here somewhere.