If I can remember the Dometic has a cone shaped gasket that did not fit right in the flange in the floor , the Thetford is a flat gasket or visa versa
anyway I had to use the Thetford gasket on the Dometic ,yep mine did NOT have a cabinet under the sink but I'm a big dude and I was cramped in there as it was so the 310 gives you a little extra room
also do not worry about the drain that is not a problem,....By the way Jim how's that working for ya shaving or washing your face in that sink???
the only thing it was good for me was washing my hands, before I sold it for my new Monty I almost wanted to rip the bottom shelf out to be able to get my head over the sink
