Ok so you want a spat in the front to direct the air at the tire and not around it? I took your advise and looked at a 2007 Toyota yaris I inspected this morning. It had front and rear spats but the front is only a small one while the rear is a little longer, I'll include pics.
And in regards to the rear diffuser why did you make it that box shape instead of a full pan? Does it direct the air out better that way?
Here's the yaris spats.
