If you are downloading a fresh new main stack from the server, and the dataGrids are empty within this, then they will be empty when it is loaded via the launcher stack.
You will need to implement some method of extracting the data from your current datagrids, storing it somewhere, downloading the new main stack and then re-inserting this data.
One way to extract the contents of your dataGrid would be something like
put the dgText of group "yourDatagrid" into gText
This would the contents of the datagrid (return and tab separated) into a variable called tText
You could then re-assign the contents of the datagrids on your new stack from this variable