OK folks, time to earn your keep!

My '90 Westy has the rear A/C shroud with 6 forward vents and two down.
Can anyone tell me how the air is ducted from the rear of the plastic
shroud to the vents in front?  Materials, shapes, sizes?  Directions,
angles?

I spied an aftermarket 'improvement' which eliminates the plastic and
places a single, flat vent on the vertical face, that supposedly improves
air flow to the front.

Please/thanks!

--
Neil2
'82 Diesel Westfalia (Ducky)
'86 Vanagon (SaVannah)
'08 170" 2500 Mega Roof Sprinter (Moby)
'90 Westfalia Subagon (SaL)
Fulltiming since August 2008
Nunquam Pendite Divendium