After loading the driver provided, Samba is not showing the 8.5x11 paper size as a selection in the Printer Properties page, 'Device Settings' tab. It only shows A4, A5 and Custom 1 to Custom 20. Using the same driver on a Windows print server shows a lot more paper size selection including the 8.5x11. Also in the Windows Print Server, the 'General' tab of this driver shows a 'Features' section which is missing from the Samba installed driver.
This is due to lack of driver initialization process. When installing the driver on a Windows on a Windows print server, the driver creates the additional forms. Since the driver if not being initialized in any fashion, it will not create the forms on the Samba server. The only way around this that I am aware of is to have a small Win32 app copy the forms from the client to the server. The missing "features" tab is probably due to enabling "Advanced printing features on the Windows remote print server. Uncheck this box and I bet the tab disappears. The advanced features are provifded by the Win32 print processor which is only available via EMF printing (unless you write yoru own print provider to intercept print jobs on Windows client). I believe there is not much that can be done without some major development work on either of these. If you are interested in solving these problems it would take some dedicated engineering time.