Stephen, just for your info I have a drilled box and only recently have come back from a long tour north through flooding rains around Newcastle New South Wales. FYI My bike didn't miss a beat once and I can guarantee the rain I came through was something else. So my point is that if you drill the whole inside the filters template, you should be like me and have no probs. Just thought you may be interested.

Staintune Pipes, K&N Pods, 45 pilots, TBS needles and 145 mains.