Hello from Finland. I've had my eco UP now for one year and it has been a great little car. I've done 23000km with average CNG consumption of 2.7kg/100km which is 0.2 under the spec 2.9kg (which just jumped to 3.8kg with the new WLTP standard.)
So far my only eco mods are VW Lupo 3L magnesium wheels with 145/80-14 ecopia tires for summer and same wheels with 165-14 MS tires for winter (still have 175-15 nokia hakka7 studs for real winter if need be)
I'm not keen to make the car look like a magnet but a clean kamback would be nice.