Hmmm I tore the rubber boot out of mine years ago stuffed my Vampire unit and my 600 CCA battery with some tools in the air box and run the wires and vac line up thru the whole where the rubber elbow used to be. Never has it taken on water and I have road in some 250 mile down pours !!!
personally I turned the hose coming from the back of the engine into a 90 and bought a cone filter from the local hardware store so it is easier to get at and clean.
but the best I seen was someone added a one way vacuum valve at the back of the engine and then pipe the crankcase gasses to the back side of his merge collector on his exhaust to burn the excess gasses.
Our very own Rocket Scientist Fred ran his up and into one of the triple filters to be recycled thru the engine. He has not experienced any problem with his method either.