The drilled hole: it is very easy to spray water up there to prevent brake line corrosion.
Water comes right down the big-ass cover and drains out instantly. Maybe a bit left at the bottom, which will evaporate anyway. Best is to spray water before going somewhere, this way water drains out and evaporates during the drive.
BTW, this big-ass cover is not sealed, moisture, water, salt can still get in on the R side.
You will like the drilled hole concept. It makes maintenance (spraying garden hose up there) a breeze.
For cross-ref purpose, the thread on brake line corrosion is here:
http://www.xoutpost.com/bmw-sav-foru...-anyone-3.html
I used 3/4-inch drill bit, I leave the hole open, no need to cover it, it also makes spraying water a breeze.