I have a grid that will generally have > 25,000 rows.  The user cannot edit any cells in the entire grid.  To minimize memory used and maximize performance I try not to touch gridRow.Cells.  Instead if I need to read a value I will do gridRow.GetCellValue.

At design time I have an UltraGrid bound to an UltraDatasource that has a certain set of bound columns.

At run time the user can choose from a list of fields.  Depending on the input I will add/remove certain unbound columns directly to the ultragrid.  After the columns are added I will query and calculate the values for these new cells.  

To assign the value I am having to use gridRow.Cells("someUnboundCol").Value = someValue.  My understanding, from your Grid Performance Guide, is that Cells are lazily created and if you don't want to use extra memory then don't interact with this collection.  

Question 1:  What would be the best way to assign the cell values for these unbound columns?  Is there any other way to do this without interacting with gridRow.Cells() and thus end up creating extra cell objects?  Is there a way to clear these cells like gridRow.DeallocateCells() or grid.Rows.DeallocateCells.  This appears to loose the values for my unbound column-cells?

Question 2:  Is my method of adding unbound columns to the grid good?  Keep in mind I will sometimes have more than 25,000 rows.  Would it be better to dynamically add/remove columns to the underlying UltraDataSource?  If I did add/remove colums directly to the UltraDataSource (at runtime) I could use DirectCast(gridRow.ListObject, UltraDataRow).SetCellValue("someColumnKey", someValue), but is this more efficient (time or memory wise) than what I am already doing?

Question 3:  Am I worrying too much about allocating/deallocating cells? 

Thanks in advance!