Forgot to say, IIRC Jules said on here a while back that a mate of his had done some trials with a racer, comparing snorkel top facing forwards/backwards and it made NO difference at all to times.
But it looks better facing forwards, so forwards it is on mine
Also forgot to say that when I had a mushroom topped snorkel, it used to get a lot of mud in the air filter from what sprayed up into the bottom of the mushroom, dried, broke up and then went in through the vents. Used to get a fair bit of finely minced peat in the air filter, just need to empty the collection pot in the bottom every so often