First of all if you can keep the racing casual you can skip half of this. However, if you get one guy that shows up and knows what he's doing and he does the following he will blow your doors off and then its not fun anymore...running foams hardcore is a lot of work.
1. Keep in mind that if you are running foams every time you have a 2% reduction in tire circumference (~1mm) you have to recalculate your roll out and adjust your gear ratio or you will be slower. This is no big deal on carpet due to low wear but on asphalt you can lose 1mm in one run.
2. As you tires get smaller you car will get lower so remember to raise ride height. When you raise ride height you reduce droop so after raising you car reset you droop. Your camber will also be reduced when you raise a car so you have to reset camber too. If you wear away more than .5mm per run you will have to do all of this every run.
3. The tires seemed to be fastest at 58-59mm in diameter. 57mm is still ok. Once you get smaller than 57 you start losing side bite and your lap time will get slower. This means that if you lose 1mm per run the tires are good for 3 runs max.
FYI, Rubber tire never change 2% in diameter from when they are new to when they are worn out. Most good rubber tires now days are good for 4 open mod runs and double that if you run 19T or Stock. After that they are 1-2/10ths off when they were new but still good for practice for another 6-8 runs.