Got it.... Another idea would be to put in one of the HP Texas Instruments "2x2" USB3 cards (as I have done in a number of HP workstations including in my Z400 and Z600). You'd want that in one of the spare PCIe generation 2 slots rather than gen 1 slot. Then you could run an external USB3 drive at full speed and not hit the 2TB size limit you and I have run up against.
That card has 2 USB3 ports on its backplane, and a standard internal USB3 header for 1 or 2 more out front or for inside the case. I once considered doing that for an internal 4TB drive mounted in the spare 5.25" optical bay, with SATA data/power adapter-to-USB3 attached to the drive's rear end. Never got around to that...... but such adapters do exist.
Also, Dan_WGBU posted here way back on some HP-tested PCIe SATA III cards, and my gut instinct would be to try another brand than what you have. I don't have experience with those at all.