Thank you to both of you for your comments.

The lens is ribbed on the inside so I am assuming there will be a wide viewing angle.

The beige part of the housing lifts up at a 45 degree angle. There are two tabs that keep the bulb holder in place. So bulb access is going to be pretty simple. I have also purchased an LED bulb. So hopefully once the third brake light is installed I will never have to change the bulb.

Mark, when you say a double wall what do you mean. Can I get access to the underside of the shelf by removing the rear seat?

Thanks.