ok, here's how we set the PSI for our slicks so it may apply for you as well.
Set a base PSI of around 20
Find a relative clean, slick patch of concrete. i.e. we use our shop floor.
power brake to leave a good footprint and measure your contact patch until a good, even grip is achieved. Solid all the way across with no thin patches in the middle or sides.
Adjust your pressure up or down until the contact sweet spot is found.
Running a low psi just to get a wrinkle wall doesn't help if your tire isn't grabbing in the center.