Door states 46 front/48 rear psi, but I think that's too high for routine driving. What suits you best? Air Pressure notice just came on and this is the first time I'll need to inflate them. Thx!

I have a 2017 SL65 but the pressures should be similar. There are four choices depending on load and maximum planned speed. Not over 155 with 2 passengers is 35F/33R, with maximum load it is 36F/36R. If you plan on diving at 186mph it is 44F/42R with 2 passengers, 48F/46R with maximum vehicle load. The sticker is on the gas filler cap.
After some experimentation I settled on 39F/36R for more responsive steering with good ride quality. But that is with the V12 up front.

Great; thx! It's strange they'd list it like they do inside the door; just creates confusion. I'm going to start by trying 37/35 due to tires not being cold when I get the air. 'preciate it, and nice ride btw!!!

Sorry about the typo above. I meant to say SL65. I do also have an S65, that gets 45psi in the front tires.
Let us know what pressures you end up liking in your SL63.

Turns out I have a bad tire pressure monitor. Air pressure was at 44 on all tires. Once I confirmed this is a maintenance item (bad sensor), I lowered all 4 tires to 40. It was running hard over bumps and now I know why.

44psi all around would be harsh in normal driving. Too bad about the bad pressure monitor. Since you are using the in-car monitor for the pressures they are usually accurate but will not measure the tires cold as you pointed out. I have a compressor in my garage and several accurate gauges so all my readings are cold in the morning after sitting all night. Suggest you drop the rear tires a couple of psi. The car will ride better and handle slightly more neutral. I hope you find the ride more reasonable now.

Thx. Will try that once I get the bad sensor fixed/replaced.