Hi. My brain is a sieve - and googling this only gets hits about putting in the 1st one - and I cannot remember back to when I did it... So please put me out of my misery. I used a OWC data-doubler to replace the optical drive with a SSD, in my mid-2012 cMBP. Question: Can I replace the HDD with a SSD as well? What connection does it have?