In Control Chart Builder, you cannot save control limits if subgroup sizes are not constant. Of course, this is because control limits are a function of subgroup size (in addition to the mean and variance). However, this makes it difficult to lock down control limits for Phase II. With fixed values for the mean and variance, control limits could still accommodate variable subgroup sizes in Phase II charting. The column property "Sigma" already exists, but we would need an additional column property for the mean.
Proposal: Add a menu option to Control Chart Builder "Save Average and Standard Deviation" or something similar. Result is column properties "Sigma" and "Average" are populated. These are used to construct control limits when the column is plotted in CCB and is indifferent to subgroup size.