Duplex Printing on Olivetti MF552 (Prevent intelligent duplex bypass)

Short Version: How do you disable 'Intelligent Duplex' on an Olivetti MFP in order to make all pages go though the Duplex unit, even single page documents.

Long Version: We have moved to duplex printing. I have it working fine on HP, Kyocera and Brother units. Most have a feature that when a single page arrives, the duplex unit is bypassed to save wear and tear and increase speed. However, when printing to Letterhead the device needs to still use the duplexer so that the print is on the correct side of the paper.

We have various Olivetti's (222/252/254/282/452/552) and I cannot get them to operate as I need. If I tell the unit that it has Letterhead in Tray1, when the print job arrives (From Word 2010 using the latest inventively named 'Generic Universal PCL' driver v2.8) the copier asks for plain paper to be loaded. The only way around that is to send the job with paper type set to Letterhead. However, the driver doesn't expose paper type enumerations and so needs to be set by the users. That isn't viable in our environment.

The best suggestion I've had from Olivetti themselves is to insert another blank page in the document. I'd actually already done that as my work around but that then leads to another chargeable click count. I can't be the only person with this problem - have I just been speaking to the wrong people as I can't help feeling I must be missing something.

Thanks for anyone who reads this far!