Spacer question

[Racer Boy]

I went to a track day yesterday, and realized I should have probably gotten 15mm spacers for the rear, because now the balance is different. Before the spacers, the handling was just right, very neutral. But now it understeers! Just a little bit, but it is a demonstration of how little things can affect the balance of the car.

[FoFoJoe]

I recently installed Eibach lowering springs on my '01 base model, all stock suspension otherwise. I'm planning on running 15mm spacers in the front and possibly 18mm/20mm in the rear.

Here's how the car sits now. I definitely want to get rid of that gap.

I'm thinking 15mm will fit in the front without rubbing, but the rears is where I'm not sure. I'm leaning towards an 18mm in the rear so I don't risk the fender as much.