Decklid extension suggestions?

[VWCw]

grill block: check.
wheel skirts: check.

decklid extension: probably?

thinking about either dumpster diving the local sign shop or getting a campaign sign to make a colorplast decklid extension. i was originally thinking something akin to the fusion 999, but maybe toned down a bit. like only 4-5 inches out. then i was reading moonmonkey's thread and there was talk of extending at least 14" out.

this is on a type III jetta, where both the roofline and decklid are basically flat. there is a photo on an em thread somewhere that shows an older golf versus jetta in a wind tunnel that shows the airflow pretty much attached all the way down the rear window and onto the decklid of the jetta (if i find the image i'll repost it here).

for the time being, here's a photo of my jetta from the side. any suggestions as to the length/general design/if-it's-even-worth-the-trouble-ness of an extension?

[VWCw]

finally found the image i was looking for (originally posted by MetoMPG):

[aerohead]

Originally Posted by VWCw

finally found the image i was looking for (originally posted by MetoMPG):

VWCw,if you compared the smoke filled wake behind the Golf-1 ( Rabbit ) and the 'Aerodynamic Streamlining Template Part-C' working diagram you'd see a resemblance between the two.
The smoke is basically telling you how the body should be formed.
The 14-inch spoiler you mentioned is probably an attempt to get the body to reach back far enough to intersect the 'Template' curve.
Any length is beneficial.For an insight into what the rear modifications can do,please check out "BOAT TAIL Drag Reduction Estimates".
You can use the SEARCH EcoModder.com or find it back on page 6 here at the aero forum.
VW has done a really good job with the Jetta but any significant drag reductions are going to have to come from reducing the wake.

[Bicycle Bob]

If the material is free, you might just want to test a few different lengths before finishing the final version. Start long, test, trim, re-test, and then maybe re-build.