HI Paul,
If your cluster only has one type workload running, you can under subscribe the core number for the node, to let scheduler think the node has only 2 cores. (Try using powershell cmdlet "Set-HPCNode -SubscribedCores" to configure it)
The other way is to have your job to allocate resource type to Socket if you have 2 socket for the node (If not, you can also subscribe the socket number for the nodes). This way you won't change the core number for the node thus other jobs/workloads
are not imapcted
A third way is put those tasks into 20 jobs, and you can put memory requirements for your job.
Qiufang Shi