Hi ccbouley
I'm not with Laminar Research, just a fellow simmer in the UK.
As a qualified PC technician, your spec's on face value look more than capable of handling what XP11 could through at them!
To rule out any possible issues here though, you may wish to download a small piece of software from: https://cpu.userbenchmark.com/Software which will 'stress test' your PC to identify any possible causes of the problem that you have reported.
The results of this test will show as a report on the UserBenchmark web page.
Further, you may wish to look at a YouTube video by the well know simmer Q8Pilot, where he advises of XP11 settings in general, in order to maintain a decent fps. Basically anything above 30 fps would be acceptable!
The Q8Pilot video can be found here: https://www.youtube.com/watch?v=mljKJnZeALM
Let me know how you get on?
Regards