I've replied a few days ago in the first topic you made on our site as well.
1 thing is really valuable of knowledge, to rule out the causes:
Do you run your UT99 at 1 core, or at multiple cores ?
It explicitly needs to run at 1 core.
I don't read in your post, that you actually checked this.
Might be very handy, to still do that!
ACE can have problems capping your framerate if its running at multiple cores.
Such things are really important to rule out before changing server settings
or even starting thinking about other things.
Minimize the game
CTRL+SHIFT+ESC for taskmgr.
Check processes tab
Go to details
Uncheck all cores.
Only keep CPU(0) checked.
*note in WIN7 and WIN8 8.1 this option won't be remembered by Windows, after you restart the process
Thats why i've included the multicorefix executable in our ClassicUT99 version.
Can you give an answer on these questions?
Not replying, won't narrow down the rootcause.