I see what you are saying. I always make my went/pressure lines bend up near the top of the tank and into the bubble if equipped and assumed all others did as that is typically in the directions. To avoid the pickup line doubling back on you is very easy, just add a brass section to the line longer than the with of the tank and then it can not. You could also place a soda straw over the outside of the tube if preferred. I'll see if I can get RCKEN to add a graphic here of this. I don't believe the vent line siphoning would appear as fuel in the carb. The entire engine would have to fill with fuel first IMO.

If anything, due to the inverted installation the tank may be too high in relation to the needle