Optimise plotting queues i7-4770

Hello, I have the following configuration:
CPU: i7-4770;
RAM: 16 GB DDR3;
2x240 SATA SSD RAID0 - after format 447GB
2x1TB M2 SSD RAID0 on PCIe adaptors - after format 1,86TB
Some additional disks(4TB,2х1TB, 750GB)

At the moment I’m running 2 queues, one on M2 disks, one on SSDs, with max PLOTS(28), 110min intervals, at the moment processor is 40-45%, ram - 60-70%.
Are this settings are OK or they can be optimised?

My test with single PLOT give me 7h for completing.
I’m plotting solo, not in pool. Thanks!