How should I do it?
it's just a game of shades, use one or two darker shades of grey to enhance the lowermost and leftmost part of the overhang to reflect the shadows, ad on the other hand use a slighty lighter shade on the right side to show that part beign hit by the light (wich is supposed to come diagonally from the bow).
the result should be something like that:
(you can keep the shading i've done without need to credit me)