Never did the 320 when I had my 3402 RL I thought it would take up too much space(too long) in there so I went with the 310 and it fits Excellent! ,only thing I had to do was get a 1 ft flexable steel mesh hose and a female to female adapter, although the stock Pex hose will fit on the Dometic you have to push the hose down the hole and it fits at weird angle and mine started leaking hence the flex extension and also the Dometic gasket did not fit my floor flange so I had to us the old Thetford gasket other than those minor things NO PROBLEM
