come off of the head with hose and use a tire valve stem drill a hole in the lower cover just off to the side and pull the valve through this hole with the fat round end on the out side. Now remove the inner stem so the water can pee out. This will give for a factory look and it looks clean at the same time.
I believe the tire stem luck used was for a grommet like yours, just removed the valve and feed the tubing through it. Pic would be nice to post though if you got one
They use a rubber cromet with a little plastic nub moulded in it so the tube can be slipped on it. It comes out looking flush with the motor case. I let my clear tube come out about 1/4 inch, looks real clean.
I didnt want any type of metal touching the motor case because of the little extra rotting problem I may get later down the road.
although i am not against the added tell tail .. i feel it takes some water away from the motor .. i know i know but its my way of thinking so instead of the homemade tell tail .. i added a water pressure gauge to mine and can see it right at the captions chair just in case of anything .. i found it on ebay new in box for 7.99 although it was an older one it was new ..