Well, just a post to say I've played STL Origins (mission 2 and from 4 till end) with FS Port 3.0.3 WITHOUT any trouble.
OTOH, STL comes with its own set of *.tbl and FS Port 3.0.3 doesn't have any *.tbm to modify them. So, although I'm no expert at all, I can't see any reason to make them incompatible if bitmaps, models and every other component have kept their old names in this newest Port version. (And even game balance should be exactly the same because Port tables aren't used).
If someone has any trouble with STL and Port 3.0.3, I can try to run the problematic mission to see what happens in my PC. But AFAIK there should only be some trouble with the removed SEXP, and this is a conflict with newest FS_Open.exe builds, not with Port.
Well I nearly forgot: I've used latest Redmenace builds (or sometimes latest CVS own-compiled builds) with media vps 3.6.8. delta with some updates and minor patches (new DIS and Fenris ...). If you have some kind of trouble I first recommend to update to this latest versions of exes and vps as they're pretty stable (nearly always).