Hi,
The SG2 has an intake temp setting which I use to keep an eye on it.
I'm thinking of adding some small holes to let cooler air into the intake which is in the slam panel just to the left (from the drivers seat) of the badge on mine. From what I've read the engine likes to be warm but have cold air coming in.
I was sitting stuck in traffic (2 hours to get home last night due to accident - its 14 miles...) and the intake temp got up to nealy 25. I suspect the radiator is having an effect there. My next mod may be a shield just behind the grill to restrict hot air rising from the radiator when stopped.
That 1.4 will be a superb eco-machine.
I've thought about the underside but whenever I take a look it does seem quite good. The rear bumper is kind of parachute like but the wheelarches on mine are filled more than usual because of the DPO big wheels. The bumper is different on the VRS too although I don't think it is significantly different.
Do you mean the tabs under the front bumper ? Interesting. Mine just match the width of the wheels but the front bumper extends quite a way under the front.
I'll watch your mods with interest