Mark,I am going up again on Sept 20 -24th. I dont know anything about the Missouri River. We are mostly up around the Waubay area. I would be happy to show you what I know about those lakes. I recently purchased a new Lakemaster chip, it works better than my Navionics. I like the shallow water highlights in red. It is possible that Lakemaster has the Missouri River on one of their chips.If you take your Puma you will get a lot of attention. Nobody has seen many Cats up in that area. It really gets their attention when you come down the lake showing some of that pad. Just be careful, dont need to donate your lower unit while you are up there. The water up there seems to have a lot of lime deposits, make sure you wax it well before taking it up there, and I try to wipe mine off when taking out each time. PM me if you want to visit some more about the area.Bill Mac