From the Sculpfun site for S30 Pro, I have no idea where, I have this:
Black Acrylic, 6mm, 180mm/min, 2 passes, 100% power, air on.
11 passes for 11mm black acrylic.
Nothing for any other color acrylic. Clear acrylic, not possible.
What I did was to etch and cut everything I could get my hand on and track the results in a google sheet. I now have my own reference for my specific 30W machine. Just be aware, that the focal depth of your laser to cut, is fairly narrow. To cut something deeper than say… 3mm you may need to adjust the laser height halfway thorough. Although you can get through thicker materials, the unfocused laser beyond the focal range of your particular machine will get wide and inefficient often making a mess. Due to these restrictions, I am uncertain if 11mm acrylic can be cut with a laser.
It can, at least with Sculpfun laser heads. They are known to have a very thin and very long focus range. Many other brands have more problems in that respect. With an S30 Pro, you can cut more than 10mm without refocussing.
Though, you are correct, lowering the focus to the middle of the workpiece will always be beneficial, no matter which head is used, also with Sculpfun.