here's my fuel dot planes they all have em none leak,if you notice them getting a little sticky a little denatured alcohol cleans the gunk out none of the ones I fly have had any sticking issues,might be because I use fuel with low castor content,you can fuel, and defuel,through them.
if you let them sit in fuel for long periods, I can see where they might get stickey, but as long as you clear the fuel lines after flying there trouble free,I happen to like them for the hidden feature they can be mounted behind a cowl and the hole just needs to be the size of the probe to fuel the plane,as for leaking if you use a zip tie around the fuel lines going into and out of the EZ fueler there not coming off or leaking there.
Hangar-9 P-51 Mustang
Hangar-9 P-40 Warhawk
Top Flight,spitfire
Top Flight P-47 Thunderbolt
the P-47 should be getting its maiden wings pretty soon looking for a calm weekend.