And no dripping down the side!

So here's the solution (at least for my 90 Westy Syncro):

I went to a hardware store and bought brass fittings that make the
transition from 3/4 inch hose threads to a male nipple that fits into 1/4
inch inside diameter tubing (3/8 inch O.D.). I pushed about 6 inches of
clear plastic (potable quality) tubing onto the brass nipple and trimmed the
free end at about a 45 degree angle.

This construction is pretty much the same as a RV water tank filler tube
except that the tubing is much smaller. The critical part is that the tubing
is small enough to fit through one of the openings in the baffle just inside
the filler hole. Seems that this baffle has a rubber flap that inhibits
water that is just poured onto it with a hose from the outside. But the tube
gets past the baffle so that the water that comes through the tube is
totally unrestricted. I can literally fill my tank in about 3 minutes! And
no drips unless you try to over fill the tank.

The exact fittings that I used starting from the male fitting on the end of
the hose are:
1 - 3/4 inch female hose threads to male 3/4 inch pipe thread (brass)
2 - 3/4 inch female pipe thread by 3/8 inch female pipe thread bell reducer
(brass)
3 - 3/8 inch male pipe threads by 1/4 inch (I think) tubing nipple (brass)
4 - 6 inches 1/4 inch I.D. by 3/8 inch O.D. tubing

Other fitting combinations are possible. The only important thing is to get
from hose threads down to a tubing with a 3/8 inch outside diameter. Most
any hardware store should be able to set you up with some combination of
fittings that will do the job. I choose brass instead of plastic because I
am sure the brass is potable quality, and not so sure about some of the
plastics.

To make the filler even easier to use you can buy a small plastic valve that
fits onto the end of a garden hose (in the garden section). It has female
hose threads to on one side to fit onto the hose and male hose threads on
the other end that fit into the first of the brass fittings listed above.

This really works great to solve a pain in the B_T problem.
Good Luck,
Bill
90 Westy Syncro
Lake Tahoe