i've heard awful things about having drains on axles. all the toyota owners shave their drains off and weld a cover over them. and ive also heard many people complain about buying aftermarket covers with drains because they get bashed and could either rip open or get so boggered up that you can't get a socket on it or an allen in there.
and also, did you have any trouble getting a good seal with the two cover bolts covered by the guard? if you drilleed them out please disreguard...