Decklid extensions/etc...

[roflwaffle]

For a cheap aero band aid that's easily removable I was thinking about a bike rack with some sort of clear material bolted to it such that the angle between the top of the car and edge was about 12.5 degrees, with exhaust routed upwards in order to hopefully fill up the low pressure area behind the vehicle. Anyone have any thoughts/comments about how it will/won't help?

[MetroMPG]

Which part?

I can't comment on the exhaust filling part.

But I think the idea of using a bike carrier for a removable partial boattail is decent. No reason it won't make a measurable difference, providing the proper angles are respected.

It's come up before around the intertubes. Nobody's done it yet though, as far as I know.

[diesel_john]

this package is worth over 10%, if i had to quess, i'd say the back is at least 3 of the 10% over stock. but you are starting probably 10% under stock.

note the rectilinear exhaust on the far left

IMHO, i would put air fences on the sides of the clear to get the most.