I've got an ARB on my XJ and have left the holes open. They are small enough not to pour water into your air box. Letting water in, they leak very slowly and would take some time for the airbox to fill the whole way to the air filter. Most river/water obstacles are relatively short and the idea is to get in and get out quickly and not to spend hours in the water.
I've had a very small amount of water in my airbox following a thunderstorm and found those holes drain the water away slowly. Pete must have had a monsoon hitting the mouth of his snorkel over a couple of hours to allow the airbox to fill up to the exent that the air filter was wet (unless airboxes on a TJ are a lot shallower than the XJ airbox)
I wouldn't swing the "ram" around to face backwards as that would just look stoooopid! But I have got an alloy aftermarket grill on mine as the plastic grills supplied seem to get ripped off easily by branches.
Oh yes and K&N 110%
