Ooh I just love debating the finer points with Gort!
And trapper_canada thought he had a dumb question.
It does indeed matter how high you route the hoses, because the lobes of the tank are below the frame rail so that the level in the tank is below the end of the vent lines much of the time. Not
all of the time (I think the bottom of the filler neck is above the frame rail) but a stuck float would never cause the tank to empty out of the vent hoses.
The other thing is, the vent hoses as routed by the factory would pressurize the bowl to 3 or 4 times the normal head before leaking gas, and I serously doubt the engine would run under that condition. I don't know that for sure though, so will trust the engineers on that point, then my own ability to shut it down when it's running poorly, and failing that, at least these bikes aren't known for spontaneous combustion.
Original design ..good
Routing straight to ground ..worse
Routing up then to ground per Gort's idea ..best. I'd do it that way if I wasn't about to change carbs.