First thing to do is think really hard about what you need to take. The Shaman ($750; www.wildernesssystems.com) is a nice little boat, but it’s not real big. Figure out what the weather is apt to be, pack clothing accordingly, downsize whatever you can, and then squeeze stuff in. You ought to be able to get most of what you need into that back compartment. That shouldn’t screw up the balance too much. Best thing to do is to go out for a quick trial. Pack 40 pounds into the back of the boat, get in, and float around for a while. The bow might be a little high, but not by much.
Otherwise, sure, get a tapered dry bag and use that up front. That will of course act like an air bag, adding flotation (as will all your sealed stuff sacks). You’ll probably want something like the Seattle Sports Cyclone Tapered Dry Sack, in medium or large ($37 or $45; www.seattlesportsco.com). The large will add about 2,000 cubic inches of storage capacity, the medium 1,200. Either way, pack the bow bag with smaller but heavier items聴stove, fuel, cookware, and things for which you don’t need ready access. In the back should go clothes, first-aid kit, lunch, water. You can also store some things in a dry bag under the deck webbing, such as your coat, camera, map, and other stuff for which you’ll need ready access.
Good luck!