[Lampoon]

If you funnel air to the box via Ram Air (hood or scoop) then you put positive pressure in the box. No need to seal it. Also I wouldnt want it sealed so water can escape.

but hey....thats just me. The Crab is a box...not just a shield.
You have coverage on all sides with the hood being the lid.

 

[Lampoon]

The bottom hole is where your intake gets its air....or are you talking about raming air into the box from above? Youve confused me now.

As for a PVC build Nate did one here: http://www.g6performance.com/forum/showthread.php?t=15697

Turned out pretty neat but Im sure its heavy.

If your just going to alter your stocker thats been done before as well. Doesnt look good at all.

Acrylic tops been done before too. Didnt look good.

I havent seen lights in the shield yet though!!

Kinda hard to be original to a car thats 5.5 yrs old.

Post up snaps on what end up with.