Custom fields are disabled in the invoice template options, setting width % to zero does not hide the column, it merely minimizes to 1 character width ?

I'd like to hide custom fields in certain templates.

Disabling "Show on all PDF" in item custom fields is not an option as they are required for other uses such as bay locations for warehouse use for sales orders but are not required for the invoices.

If this can't be achieved, can you please give me a deluge example of how to set each invoice line items custom field ("Bay") value to "" so that it does not appear.