I tried all kinds of pressures on my stock tires w/ the SRT-4. You CAN go too low. I initially tried 25psi and did pretty well. I dropped to 22psi and my times got worse, so I went back to 25psi for the longest time.
Then one day I lowered them to just 28psi and cut my best 60' times ever (on street tires). The real answer is, it depends on the tire and the weight on the tire. Try different pressures. If you have a track like the one I go to here, where you can get a dozen or two runs in a single night, then run 3 times (checking the pressure before each run to make sure the pressure hasn't changed). Change the pressure and then run 3 more times. Compare you average and your best 60's and go from there.
With the stock rubber, you will have to experiment. Drag strips usually don't hook up as well as the street with stock tires. Unless it's totally un-prepped....in other words, they haven't sprayed traction compound all night. That stuff really only works for slicks.
If you really want to play, get some drag radials. HUGE difference. With a burn out, they will actually bog the engine.
And forget slipping the clutch a lot....unless you want to install a new one.
Today i was at the strip and the first two runs sucked. i ran a 15.4 with the stock air pressure witch was about 40 psi. i couldnt hook up what so ever. i droped it down to 25psi and i ran a 13.6 consistantly. so 25psi is a really good number to start at i would have tried lower but my 4th run i redlighted oops.