Could you edit the Custom Layout, via the addon folder.
Rather than doing it in game?

I have thirty seven names on line one.
But they're all across my accounts.
So will never have more than five on at the same time.

And then the entire grid is set for a maximum of forty players.
Which could actually have some not displayed, if I were to run a 40-man BG.
But only do it with say two or four toons (who are in column one).
With the rest of the raid 36 or 38 toons, in the remaining seven columns which can accommodate a maximum of 35 additional names beyond my toons in column one.