hey.....I fitted mine last weekend, had similar contemplations while sitting on the floor along side the bike.
Assuming you sitting on the bike, I ran the fuel line from the right petcock under the tank, above the carb and behind (towards the rear of the bike) the "throttle cable connection to the carb".....although there appeared more space infront....to the Y-junction and onto the carb.
The reason I did that was because I wanted the fuel cable out of the way (ie: under the tank), I wanted the most direct route to put the least effort on the carb when drawing fuel (there is a slight incline in the tube flow doing it this way but this hasnt seemed to affect its working), didnt want it interferring or limiting the throttle cable when riding/ accelerating/ decelerating etc...and didnt want it resting on anything too hot (ie: engine).....Im not sure what it takes to become a fire-ball
So far all appears to be working well.
- You also got the lumo purple fuel lines ? - funky
Once set up.....let me know how it goes starting the bike, took me a while to get it operating properly.....and the air out the fuel lines
....but hey, Im a novice.