The inflation pressures stated by vehicle manufacturers are the minimums, and I wouldn't use less. If the ride feels too stiff, fix the suspension and don't mess with tire safety. Especially during the transitional periods of the year, when ambient temperatures can vary widely, check pressures often. A good rule of thumb is that your tire pressure will change by 1 psi for every 10°F change in temperature. For example, if you set the air pressure at 40 psi Monday when the air temperature was 70°, the pressure would be approximately 37 psi on Wednesday when the air temp was only 40°F.
In the overall scheme of things, it's much safer to run a little too much pressure than it is to run too little. Less pressure equals more tire flexing and squirming, which leads to a buildup of heat in the tire. That in turn can lead to catastrophic tire failures. Think back to the big flap many years ago over Firestone tires on Ford Explorers failing. The cause was low inflation pressure and a tire with an insufficient safety margin built in.
Jerry