Russell,
If you have chased a ring and cleaned up the back, you should start by marking a center line starting at the most narrow spot on the stave. Find the center there and draw a line in pencil down the back of the bow. You should be able to see the lines in the grain that run lengthwise up and down the bow.
After you have marked the centerline, make sure it leaves enough width up and down the bow for your design. If not redo the centerline more to one side or the other.
If the centerline is good then mark your handle and limbs with their corresponding widths.
Once you’ve done that, remove wood to get to your desired width. If you’re using a draw knife, go slowly. When you get close to the line, the blade of the draw knife will tell you how close your marked line is to following the grain. Be careful not to let your draw knife dig into the limb past your width line.