Thanks for the reply, pcyrgalis...
My issue lies with the filler hose and where it meets the filler tube on the tank.
I'm using a marine-grade fuel hose with a hose clamp and don't seem to be able to prevent leaks while fueling unless I use a funnel with a spout that is long enough to get past the spot where the top of the filler tube sits inside the filler hose.
Just curious about others' experiences and fixes.