650F Vault/FLARE drive upgrade

Hi, 

Curious if there's a procedure to increase the vault/FLARE drives from say, 3.84TB to 7.68TB disks.  A customer of ours is wanting 25x 7.68 in one chassis, but our first 4 disks are 3.84TB.  We used to do this kind of thing on old clariion systems by swapping one drive at a time and waiting for a rebuild, but I feel like this stopped working at some point.  Anyone ever tried this kind of thing before?

Thanks,