Making a defrost duct

I'm trying to install some defrost ducts in my car, but space is very limited. The standard molded plastic fittings are just too big.

What I have to do is fabricate a very low profile duct sytem myself that would hug tightly underneath the dash and cowl so I will have room to run the AC ducts. The defrost exits the unit facing the firewall, and it's about 6" forward from where the defrost will exit the duct through the dash.

I want to use some sort of plastic similar to what the condensor unit is made from. I can use the flexible duct to turn the 180 degrees to get the airflow headed back toward the dash, but from there i want to use plastic. From the collector, it will be about 4" before it has to split into the individual ducts - which I'm thinking about using something like 1" X 1.5"w rectangle tube.

Does anyone have any tips about what material to use, where to find it, and what type of glue would hold up?

I would suggest not using ABS, since most glues will not adhere to it. Sometihing made of polystryene would be a better choice even though it's generally not as stong as ABS.

Have you looked at some of the shop vac nozzles? There are some really skinny ones that are molded with the hose attachment flange. Every so often, I see one and think that it would make a good defroster outlet.....but then, I dont have a defroster.

Also, do a search for an air knife such as
http://www.air-knives.com/?SRC=ggl&VAR=man
they can be essentially a long tube with a slot cut in the side and positioned under the windshield. The pics on the site may give you ideas. Air volume and speed are concerns to make the thing work.

mike in tucson