Shelley,
Also, I cannot change the data type of the additional fields I have added in Method (Not QB Custom Fields). I can change the field length, but not the data type. There does appear to be a drop down arrow indicating this widget might allow changes, but no luck getting it to work.
About your Custom Screen. I would think that for Customers, all your changes would need to be to the Customer table, regardless of which screen you are using. As I understand it, you must create a new screen to make changes to the Method designed screen and the new screen will automaticaly point to the same shared Method table. New fields are added to the table, then available to be used on the new screen or any screen that has the Customer table as the primary table. Fields from other tables are available if there is a link from the primary table to the detail table.
It would be nice to change data types on the fly, but there might be a good reason this function isn't working. Luckily it's pretty quick to delete and add fields.
Something to consider is that any screen that is using a field may have some data type dependent functionality, so even though the field may not have any data in it, there may be a screen created that is using the field. So, when the data type changes in the table, some data in the screen definition may need to change. Method may be choosing to avoid the issues of this cascade of changes to the screens which depend on the table table definition, even though data is not changed.
Of course, this is only speculation on my part, I'm sure one of the Business Consultants will give you a better answer.
Cheers,
James