Should be fine since 7.1 can also run a matching ndmpd version 3 or 4... qtree snapmirror may also be a good route since it supports multiple incrementals. If you don't have qtrees you can specify /vol/volname/- as the source to grab non-qtree data then put it in a qtree on the target. ndmpcopy only supports dump levels 0,1,2 so you get 2 incrementals after the full.