So we've reached the point where our 32->32 bit data motion (vFiler migrations) are almost complete - (pending one vFiler stuck in "Migrate Failed" state case, and a previously  fun flex clone vFiler)
we purposely destroyed the destination (> 19Tb 64bit) aggregates and recreated them < 16Tb to work around 32->64bit data motion incompatibility
Next we will initiate non-disruptive 64 bit aggregate upgrades by adding disk (the only currently supported method)

Its beaucoup hoops, but we are almost there - our goal is to data motion off all vFilers btw partner clusters to complete our flash cache hardware upgrade

thanks

Fletcher