You need to log into your world community grid account and select device manager and then device profiles and select one of your options at that point. When you go into that screen toward the bottom there is an option under "Project Specific Settings" where you can set the maximum number of Clean Energy Project work units.

Be aware that its set to one by default due to the amount of memory each one can take up and the amount of hard drive strain they can cause if you have allot running at once, especially if they all start up at the same time.

I might try 4 with that setup and see what happens and possibly go higher. (You do at least certainly have enough ram to go pretty high if you're not doing too much else with the computer at the same time.) Having said this I'm not really an expert in this area and others may have more specific recommendations. To be clear on the hard drive issue, its not the size of the hard drive which is the problem, but the nature of the program ending up with allot of data needing to go from it to the computer memory at the same time which can lead to bottleneck issues.

I have gone measurably higher than this on one of my machines, but I am willing to tolerate a certain amount of issues from time to time and intentionally manually stagger the completion of individual work units when necessary.

Mu suggestion, look at the CPU time and the elapsed time when you are running just one CEP2. Then increase it to run two and compare them again. If you run too many, you may/will have resource issues and more and more processing time will be lost as you increase the number of CEP2's running concurrently.