Okay, I don't know if I did anything right, but I added now few things, to front I made small lip, barely visible in a photo, then I added wheel well covers, rears need still bit of work, some support so it does not look like curtain, but I'm yet to come by appropriate scrap metal.
You can see in photo that my kammback attempt, I checked that car's sideline is straight in gimp and measure bit under 11 degrees for first section and around 13 degrees for latter section (that has red metal supports). I think that those red parts could of been larger, but metal piece was so small that I got barely those two out from it.
Added new 3rd brake light too:
Yes, car is covered in clay, mud and who knows what, it is this time of year and these roads, no point washing car until about month or so.
I did some Flow Illustrator testing, but I don't think that it really tells much, front lip could be lower, but it is already around 60-70mm from ground and is touching ground on bad roads, good thing it is still flexible, might need some supports to that one too.
Black material is vinyl carpet, used in house floors, this one had lot of mould and it was rather small piece, just enough for car.
Rear belly pan and sideskirts are perhaps next that I will do when I will have time again. Underside is horrible, rear bumper is like U-shaped air brake, there is spare wheel too, I'm thinking of leaving spare wheel out and getting one of those bottles that promise to fix tyre, then I could put cover to that area so it would be smooth, probably largest effect.
I also did the ultimate mod:
