The form always inherits whatever page size the printer is set to, or whatever the printer tells the application what it's page size is.
So are you saying that if we edit the form and set the default to a different printer, the page size should change?
We're not complaining to you about the printer drivers being incorrect, but rather that you are relying on them to set the printable area of the lables, and it doesn't always work. As you say, the driver settings are not always correct. So why not use a method that is always correct and set the page size to a standard A4 and allow the user to change the margins? It's just a suggestion as to a way you can improve your product to make it more user friendly. It's up to you whether you want to do that.
We already have a workaround which involves sacrificing 5mm of our labels. The only other alternative seems to be to change our printers and hope that we get one that not only prints to our labels (like our current printers do using Word), but also has the correct settings in the printer driver (which apparently our current ones don't - and neither do many Epson or HP models according to the previous post).