I get a memory low disk space message since its only 20GB for the virtual OSX. Will I be able to fix this once I have it native?
I don't understand the reasoning behind that question.
The low diskspace warning pertains to the OS X installation on your virtual machine.
Therefore it is completely unrelated to the actual installation that you are about to perform.
Although obviously, if you choose to install OS X onto a 20GB partition you will see the same error message once it starts running out of space.