Is 14 1/2 okay?

It depends on what the space between the wires is, rather than the overall size of the grids. They should not be over 1.5" squares, as pigs could get their heads trapped in the larger holes.

Some brands are 14" some are 14 1/2". Target grids must be the old ones with 9 grid spaces in both directions.

Yes and the old target grids that are 9x9 squares are 14 1/2" as well, but honestly I would go to somewhere other than target to get the grids.