No. Once a Contest has been created, you may not alter the shape of the contest by adjusting the number of rows and/or columns.
By adjusting the number of rows or columns, you would essentially potentially be relocating squares that players bought into their new home in the smaller or larger contest.
We consider it far too presumptuous that the player who selected a specific square in one shape would be perfectly fine relocated in the newly-shaped Contest.
This can be achieved by the commissioner manually adding Offline Players in the new Contest, but those players will not be physically linked to a user account. That's the best we can do, rather than have the commissioner move a linked user around the grid potentially without their permission.