The problem with the VSX migration is that you will need to migrtae all 6 VSX related CMA's at the time, I did this a while back from different R77.30 MDS servers into 1 setup with about 30 VS contaning CMA's per setup and about4 CMA's with the VSX Gateways in them. Was quite a job but there is a check to mke sure you know what you are doing.
Most important part in this case would be to make sure the CMA Names and IP's remain the same. Next (on R77.30 you need to create a empty file at a specific place with a specific name. I don't expect that this was changed. As long as you know what you are doing that is the correct method.
I was looking for the filename and location but was unable to find it yet.
Regards, Maarten