Hi MaXxivelCT,
Thanks for posting.
How many monitors do you have and is enhanced taskbar enabled in Start11?
As Neil has asked, this information would be helpful. Currently this may not be possible if you are using over two monitors, but he is certainly the expert regarding that.
For your issue here, I'd also like to verify what steps you're taking here against how I've been able to get it to work on my end, with your same Windows build and Start11 version.
To make the taskbar smaller while keeping the start button aligned in the center, here's how that should currently work:
1. First, any change to your taskbar size in Start11 with this version of Windows should tell you, "Enhanced taskbar mode must be enabled". To do that, you can go to the Taskbar tab, and switch this toggle to "On".

2. Allow the software to restart explorer to apply this change by then clicking "Yes" at the resulting pop-up:

3. Here, you may notice the Start Menu and taskbar default back to the left aligned position. You can try changing it back with the following Start Button option for 'Center aligned' (note, this is experimental and may not work with more than 2 monitors):

4. Now, go back to the Taskbar and find the "Taskbar size" option, and check if this will allow you to change it to Small.

I hope these steps work for you. Again, as step #3 states, this may not work if you have over 2 monitors. If not, feel free to reply with what you're seeing differently on your end. A screenshot image of any problem areas can be pasted directly into your reply.
Best regards,
Adam McGuinness
Stardock Customer Support Specialist