Custom paper sizes

[FrintonFogey]

I recently purchased a Brother MFC-J6720DW printer and want to be able to create a custom paper size for a non standard document (210mm x99mm) but cannot find a way to do this. My old HP printer handled this without any problems but this is all different on the Brother. I am running Mac OS X 10.11 El Capitan and have tried Pages, Numbers and The Print Shop 3 but no luck. Whenever I try to print the document, a message is displayed “Invalid Paper Size Change the Custom Paper Size to the correct value, or choose "Scale to fit paper size”. (Please see attached screen shots)
I have contacted Brother Customer Support who tell me to make a selection from the Paper Size dialog box but this box does not appear on the Print Options displayed. I have downloaded the latest drivers from Brother, deleted the printer and installed the printer but nothing changes and Brother do not seem to understand the problem.
So, if anybody out there can help I would be extremely grateful and it would save my sanity!!

 

[FrintonFogey]

Update on this problem - Have been in contact with Brother Technical Support and they have told me this is not possible with this printer!!!!!!!!! Apparently you can only chose a paper size from the list of standard sizes they supply, custom paper sizes are not possible. So, this printer is going straight onto ebay and I will now purchase a proper printer.