OK, here's a pic I had:
http://i880.photobucket.com/albums/ac4/mxw128/RVSewer.jpg
The black tank and grey tank outlets are solid, and one piece past the gates. The bottom of the outlet sits right against the movable door on the bottom. So if you can straight off the outlet, it will hit the lip of the compartment. The distance between the front of the outlet and the inside edge of the compartment lip is too small to fit an elbow and it's smaller than the diameter of a typical flex pipe.
So I can force a flex pipe from underneath and connect it, or go over the compartment lip and connect (there will be a hump in the hose that will hold some fluid) but either way it seems that the connection always leaks. The mating surface of the outlook appears to be smooth and I don't see any burrs, cracks etc... Tried new seals and doubling up on seals too...
(posted the pic using the advanced posting below)