There seems to be a lot of bumpy paved roads in our city and even in the C Mode
I find that the S Class should be smoother.
Is letting some air out of the tires the way to go?

 

not a good idea in general. Bad for your tire wear and performance. Bad for the handling at speed. Bad for clearance.

I have 19 inch wheels and find 35 to be good pressure for the factors listed about.

I doubt you will get a noticeable improvement in the ride quality. If its an issue versus other S classes you've driven perhaps there are issues with the suspension in your car, such as bushing or struts.

 

First off, switch to 18" tires if you have 19's. That will be the biggest difference you can make. The car is certainly not a floater, Lexus has that covered. I find my car to be a little on the firmer side which is a trade off for amazing handling for a car of its size. I would not recommend dropping air pressure, if anything you could risk rim damage. I find in my Escalade that the ride gets worse when you drop the pressure. I don't know why, maybe the truck bounces more or something, but I can tell when it is off by 5 psi...

 

I agree lowernthe presume will damage the wheels!!