Keep the wood the same thickness all alongside the barrel, so that the stock then exhibits the same swamp as the barrel. It will look good. But remember that you have to deal with the nosecap. This can determine the shape of your forestock to a large extent if you use a commercial one. Keep in mind you do not want your ramrod to get that "hung out to dry" look with a big gap between it and the nosecap. And that you'll have to transition your forestock shape near the muzzle to flow into the nosecap profile.
When you get to the nosecap, you have a decision to make. Not sure if you're using a commercial nosecap or making one. But the barrel is still flaring dramatically there. You'll need to decide whether the nosecap will flare toward the muzzle as well (follow the contour of the barrel)or be straight. If you plan to slip the nosecap on, it's hard to have any flare.
To get the flare you have to pinch the nosecap on, not slip it on. The brass must be very soft for this to work and you have to do it with the barrel out of the stock. Last but not least you have to be careful to not break the thin wood that flanks the barrel at the muzzle. It's best to make a little wooden "fake barrel" to fill the barrel channel to support the sides of the stock. Then it is possible to bend the blass nosecap into place and even curl it down inside the barrel channel at the upper surface of the forend. Then rivet in place and you are good to go.