Perhaps you could describe your workflow? I mean we could better provide advice if we know more about what you are doing.
General tips:
* uCreate Print and uPlan set the data type only for csv/txt/excel because those file types don't define data types. - IE if data type it is critical, use SQL, Access, etc which use strongly typed data.
* uCreate Print and uPlan set the data type when you link to the txt/csv/excel files. They look at every field in the column before setting a type. IE if it finds one cell with text or padded numbers, in a column that otherwise has only numbers, then it will set that column to text data type. - Therefore, I suspect that your workflow is using some temporary data file and then changing to another data file which has different types of information in the same column?
* As you suggest, when you use uPlan you can change the data type of the field in the recipient schema if you know that the data source will change and will have a different data type in future.
PS: having a dummy row should not affect your reports. options:
1) after linking to your "dummy data file" - you can relink your document to a different data file. - the adors and recipient schema are already created.
2) even if you add a "dummy line" as the first row - your production should be from record 2-n - that way, all your reporting is showing only those valid records which you printed.