I always have a hard time bending tuding around from the stopper down and to the front corner of the tank, then bending tubing up to the top for the vent, then getting all that tubing in to the tank when I install the stopper. So I use 2 clunks, it's easier for me, YMMV.

I used a Dubro fuel fitting for a little while, and had no problems with it, but I wasted the plane it was installed on, and I haven't put one on any of my other planes. I understand they always work well at first, but wear over time and start to leak air, but I've not seen it in person. I did find the odd size fuel nozzle annoying to use, espeically since I have a number of planes that don't have the fueler gizmo.