Space is at a premium on the console of my Tracker PT 170, so I have always liked the small 3.5 screens on there. I am thinking about getting the new Lowrance Elite 4 DSI for the console, does any one know if this unit has traditional 2D sonar as well as the DSI ? I am not sure I would be totaly comfortable with just DSI.

Both the Elite 4 DSI and Elite 5 DSI are downscan only, no 2D sonar. With that said, I prefer having both 2D sonar and downscan at the bow while actively fishing, but I very rarely run 2D sonar at the console. DSI will work very well while you are idling and looking for places to fish.

Do any of the Elite 5's have DSI/2D combo?

No, with the Elites you have either 2D sonar, or DSI, not both.

farmer, I have a PT 170 TX also. I still have the small Lowrance unit installed plus a couple of more units at the console:

My setup is this, (the Lowrance is behind the unit on the right and I use that with an Alumaducer when I want to).