Change of motor and the roofie was wired through the boot and sits on the rear of the roof .last sign sat middle just before door posts .Inoticed that the handling of the car was effected at speed by the signon the rear of the roof .Does it act like a spoiler and force the rear of the car downon the road .I rewired it and moved it forward .Any body else experience any difference in handling by moving the roofie ,
It's a Renault, get used to it. 
Silver I can see the drag co efficency is effected but no figure for downward thrust .Can you give the figures a look over and see if you can formulate a figure for downwart thrust ..Thanks 
The Irish roof sign causes about 5% increase in fuel consumption. It's why the NTA recommended removing it on long distance runs..
I changed to a smaller rroof sign ( €130 from PSV.IE)
Because of the aerodynamic grooves on the PRIUS roof.
I'm not sure if I'm saving much more, but it's aesthetically more pleasing.
European roof signs are about the size of a letter box, which makes sense.
Now if only the Irish could make it compulsory for the sign to go off when the meter is engaged...
