Can't change HW Buffer Size

I recently upgraded from PT8LE to PT11.



I'm trying to reduce the hardware buffer size from 256 samples to 128, but there are no other options available in the Playback Engine. Everything else seems to be running ok.



My hardware is a Roland Quad-Capture. Advice?







My Tech Specs

Operating System: Windows 8.1 64-bit

CPU: 4th Gen (Haswell) Core i5 3.5GHz

Graphics/Video: Intel HD Graphics 4600

Maximum Resolution: HDMI: 4096 x 2160 @ 24 Hz, 2560 x 1600 @ 60 Hz; DVI-D: 1920 x 1200 @ 60 Hz; VGA: 1920 x 1200 @ 60 Hz

Memory – Included: 8GB DDR3/1600 (4 slots/2 filled)

Plus: 2 4GB1600 - Lifetime Memory PC3-12800 DIMM 4GB

Plus: 1 InstallRAM - Install: 4gb1600

Memory – Max: 32GB (install in pairs)

Storage – Included: 1 TB Seagate Barracuda (SATA 6.0 Gb/s)

Optical Drive: DVD-RW

USB Ports: 4 x USB 3.0 ports (4 rear); 4 x USB 2.0 ports (2 rear, 2 front)

PCI Slots: 1 x PCIe 3.0/2.0 x16 (x16 mode, gray), 3 x PCIe 2.0 x1

Video Ports: 1 x HDMI, 1 x DVI-D, 1 x VGA