Long time update..
In the end I went with some Audi 80 hubcaps that I got for 5 euro
I did make the front section of the belly pan last year! Using parts of the Volvo kammback. Did make some difference in windnoise. Also made some panels for the lower grill.
With these mods I got around 12.5:1 or 13:1 km/l pretty consistend with the G3 lpg system on a 1.6 liter engine. However, the taxes and insurance for G3 are high, and I'm not using the car much.. So it's time to say goodbye to this Peugeot and start looking for a different, smaller car. I really like the Peugeot 106 with a 1.1 liter engine, that should get 20:1 km/l without mods. I would like to try and see what can be done with one of those.