@Stephen-Tunney I am not an expert with pip however I suspect the error you are getting is indicating that you are running out of available RAM space. Using the extended overlay method you reference only increase available file system disk space not available RAM space.
However, there is a technique that will increase available RAM space by creating an additional swap partition on your flash drive and mounting it as swap space. I have produced some documentation on how to do this: 0_1472078693377_Creating Swap Space on the Omega.pdf
I run like this regularly with a 1GByte swap partition with no problems and plenty of RAM space.
Alternatively, you could wait till the Omega2 Plus is available (https://www.indiegogo.com/projects/omega2-5-linux-computer-with-wi-fi-made-for-iot#/) - this will give you twice the available space compared to the original Omega (or the forthcoming Omega2)