Well, the shields should wrap above and below the ship, not just be in an arc around the horizontal plane.
I would imagine with that set up, facing directly towards an enemy vessel would take most fire on the foreward shield, but if you angled to where your ship's underside or top is towards the enemy fire, maybe there is a chance that the fire hits any of the shields, weighted by the actual angle, since all 4 shields would intersect in the center area top and bottom.
Agreed that 6 shields would represent that better, but I'm just speculating in hopes that we are not forced to fight only in 2d when in space, can't wait to see how it is actually working.
Hoping that z axis makes a difference in combat though, yeah.
I look at it like slicing a round Cheese into four equal slices -- as you said, the forward shield would cover the 'forward top-center-bottom' angles.