Shooting someone and hitting someone with a thing you are holding are fundamentally different. The shootee has no input in the exchange other than where they happen to be standing.
Consider cover in terms of 6ths of a person. For each 6th of a person covered by non-shootable scenery give the shooter -1 to their skill. So if someone wants to perforate me, but I'm merely sticking my head over a wall they would receive -5 to hit me.
Bob the Bowman has 5 Skill + 3 Bow Fighting - 5 for my cover = 3. He would need to roll a 3 or less to hit me in my curious head.
SHIELDS - Treat them like any other kind of cover
AIMING - Take a penalty to the shot as if the bits you don't want to shoot are covered.
PINNING - When rolling damage with ranged weapons that fire arrows or bolts or similar, if the die roll is even the projectile is stuck in you. It counts as an item for encumbrance purposes and deals d3 stamina damage to remove unless with a Heal test. Some weapons have a better chance of getting stuck in you, like javelins.
There you go +Oli Palmer