ive just finished makin a diff cover, modifying the plastistruct method Arun posted.

i used layers of plastistruct to build the sheild kinda around and into the diff, hopefully making it harder for dirt to enter.
not got a digi cam so im affraid i cant post a pic but i quicky drew up some info for it.
sorry for its utterly poor presentation lol, the holes are supposed to be in the centre of the circles , but i think i got the basic info down.....