Boots arrived and they are shape wise as good as I estimated. One problem migth be that the tip of the rubber boot migth be too stiff. It flexes but takes reasonable force to do that.
Conserning the positioning it still needs tweaking between the car and 3d model. I need to double verify the tire contact patch width and how apart the tires are actually from each other.
But overall it looks already very promising. Target is to direct air 10-20mm past the tires on both sides of the tire...
Height of the boot is 60mm which I think is pretty ideal at least for my low Audi A2. Height even increases 10mm when going towards the tire like it should. Still I will build extra 10mm lip at the end so total height will be around 80mm.
The smaller shoes are planned to be installed at rear but will see do I just use pieces from the bigger boots or what will be the best looking vs functioning solution.