It looks like you can sort by Name or by Index.
Not sure what the difference is, but the author recommended (on Curse) to sort by Name, when I asked for a fixed sort order across multiple accounts.

You could easily amend my sorting to something like this:

Tank
DPS,DPS,DPS,Healer;NAME
1,2,3,4,5,6,7;7/5;NAME;NR

Might have to tweak it a little.
You'd know the syntax is working, when it displays the tank in column one.
The rest of your toons in column two.
And the rest of the raid in other columns.

Maybe an addon like MoveAnything would let you reposition frames.
Not sure if that would work with a specific Grid frame or not.