I have a roll top desk and I need to close it so I require a very small monitor. Nobody makes a primary monitor under 17" and I need SMALL. I played with a Double Sight usb monitor when I had Mavericks and it worked pretty good with a VGA dongle (a resistor across pins 5 & 6 to simulate a primary monitor). Screen resolution was an issue with only a couple of applications so i could live with it. Then I upgraded to Yosemite and that put an end to the USB monitor. I get pinwheels constantly and the Mini runs so slowly that I can't even start up most apps. its like the USB is sucking up all available resources full time. I picked up a Fit-Headless 4K hdmi plug to simulate the monitor, but the same results. Its not a screen resolution issue and my knowledge is too basic to understand or figure out what is happening. if anyone can shed some light here it would be greatly appreciated.