In this situation, all you have is the "Old" 200DX, so use it!!..Although I have a newer unit with SI and DI on it, I rarely use it. Sunday was the first time out in almost 5 months and I went to Blackshear..I haven't been to that lake since January. I started trolling some flats looking for fish and found nothing. As I worked my way to the channel, I started seeing fish on my screen. As it turned out, they were hanging around the ledges and once we found them, we put a little weight on and got down to them. Had 23 in 1 1/2 hours. So basically I guess I am saying that relying on your fishfinder is what you are gonna have to do unless someone just puts you on the fish. That Hummingbird may be old and in gray scale, but I bet it still picks up the fish when you go over them. Sometimes we don't want to put faith in something old but I have seen many times I questioned the newer stuff...Us old farts still work....well....Some of us do!!Rofl...But to answer your question as to where to start trolling, right now I would start in the channel and the ledges looking for fish...Then go from there...In another month or so, I believe you will start finding more fish in the flats and off of points. When you find the fish and determine what depth they are holding at, make whatever adjustments you need to get the bait to them...Just my opinion...Good Luck!!