At this point you've got 15 GB worth of free space to work with IMO - it seems like most 16GB drives end up being just shy of the total size of the image. Might as well consider 32GB drives to be the standard and put some more useful stuff on the image!
Moving to 32GB drives is an interesting thought. It would (seemingly) open up a lot of new future avenues if there is no technical limitation I am ignorant to.
Btw, I'm all setup and running with the first rig (with 2 cards until more come), fullzero. Thanks for all the help. I really can't say that enough. I'm all in on nvOC. Looking forward to what the future brings.