That is a classic vacuum pod design!
A couple of suggestions if you want a vacuum hold down for very accurate work.
There needs to be a positive stop, so the Z-height is always accurate. The easiest way to do this is to have a gasket that will compress enough that your workpiece sits directly on the vacuum grid. If the workpiece is sitting directly on the gasket with no positive stop, then the z-height will vary depending on the strength of the vacuum (the gasket can deform unevenly).
To go along with this, you want the vacuum hole to be in a groove, rather than on the top.