I have been running my iMac 2011 with a 1 TB drive with 2 patrons for years.
I did it because I still needed / wanted FCP 7 running … and yes, it is on Mountain Lion.
I have each on a 500 GB partition. I would think that 200 GB would be fine, yet have not done that.
Drive Genius is able to repartition a hard drive on the fly. The key part is that one first does a defrag
on the drive to tighten up all the files before the repartition. This could take awhile.
A carbon copy clone is recommended as a backup. Last week I did another clone of the Mountain Lion partition,
just for fun. I have not used FCP 7 in a few years, so it is just sitting there. I know as soon as I delete it I will get
a call to use FCP7.
I have enuf room with 500 GB on the FCP X partition. Why? Because I put all media on external hard drives.
Sometimes I save output to the internal drive.
So, yes, I have successfully run both systems for a few years now.
FCP X 10.2.3 – user since FCP 1.25
iMac mid 2011, MBA mid 2012
iPhone 4
HVX-200, Shure wireless mic
Miller Solo tripod
Advanta-Jib