Ok i am reporting back. Apparently running dukes carribean creates new files that magicdosbox isnt doing in the process. but running the latest svn of regular dosbox on pc does create those files. i found this by digging through the vogon forum. i simply experimented on regular pc dosbox, got the files, and copied them over. i have no idea what difference that makes, but it worked! another duke expansion successfully installed on magicdoxbox! and legally too, no downloading of roms. idk why but i find that especially satesfying, when you take a game you legally bought for pc, and get it running on hardware that didnt even exist at its time of creation.