By all accounts it should be possible. With a few terminal commands, partitions can be "fused" as has been tested on the hdd side, so there's no reason that it shouldn't also work on the ssd side. I haven't yet attempted it and I'm not sure if I will or not. Though I have put the 256GB rMBP ssd in and that works fine (windows 8 is installed on it). I also have the 512GB 2.5" M4 ssd in place of the hdd (Mac OS). ...I could gain a bit more storage space and about £200 for the M4 for a small trade off in overall disk performance/noise/life ...but then again, I finally have everything setup and running nicely and I'm nearing my file migration pain threshold as it is. Installing Windows 8 (upgrade edition) without a DVD drive. Not. Fun.