Custom Letter Size - How to specify?

Just purchased the Dell 3110cn laser printer. So far everything seems to be working well. However...

 

I've created a custom paper size in MS Word 8.5x 5.5 for a series of postcards I need to address using the mail merge capabilities.

The paper size is set, the format is landscape and I saved the document as a template.

 

When I attempt to run the print job using the MFP tray, only two postcards are printed, then I get an error message stting that the media is the wrong size. I've been through the Dell menus (on my PC) in an attept to specify the correct paper size, but can''t figure out how to adjust the size.

 

The only place I can see where it may be possible to change the size on the printer is on the main laser properties menu in the drop down boxes for "paper size" & "output size". However I don't see how you can associate a specifi size with the custom sizes in the list.

 

Hopefully this all makes sense and someone can provide an answer.

 

TIA

 

 

Steve