modmanger doesnt compress objects directly, just the file. So your need to use x2bc as it does a special compression for bod/bob's (so they load in very fast). x2bc however can be a little trickly to get the correct parameters, so your probably setup a small batch file to do compression and decompression.
I would paste my batch files, however I lost them moving pc's. Try something like this:
x2bc -c --bob "swordfish2.bod" "swordfish2.bob"
Oh, and you only compress objects not scenes with x2bc! After you compress a object with x2bc, just add it and the scene to your dat/cat with modmanger.