Comment 3 for bug 173857

Please keep me informed how you like to solve it.

My immediate idea is that you need additional paper size definitions
using so called "qualifiers" - see the Adobe PPD specification
for duplex printing in your PPDs together with matching constraints.

For example here only for A4 something like
(derived from HP-DeskJet_6540-hpijs.ppd):
-------------------------------------------------------
*UIConstraints: *PageSize A4 *Duplex DuplexNoTumble
*UIConstraints: *PageSize A4 *Duplex DuplexTumble
*UIConstraints: *Duplex DuplexNoTumble *PageSize A4
*UIConstraints: *Duplex DuplexTumble *PageSize A4
...
*PageSize A4/A4: "%% FoomaticRIPOptionSetting: PageSize=A4"
*FoomaticRIPOptionSetting PageSize=A4: " -dDEVICEWIDTHPOINTS=595 &&
-dDEVICEHEIGHTPOINTS=842"
*End
*PageSize A4.Duplex/A4 for duplex printing: "%% FoomaticRIPOptionSetting: PageSize=A4"
*FoomaticRIPOptionSetting PageSize=A4: " -dDEVICEWIDTHPOINTS=595 &&
-dDEVICEHEIGHTPOINTS=822"
*End
...
*ImageableArea A4/A4: "9.72 36 585.28 833"
*ImageableArea A4.Duplex/A4 for duplex printing: "9.72 36 585.28 813"
-------------------------------------------------------

By the way:
The above values for A4 from your HP-DeskJet_6540-hpijs.ppd
for DEVICEWIDTHPOINTS and DEVICEHEIGHTPOINTS
seem not to match to the ImageableArea (i.e. what is set for
Ghostscript seems to be bigger than what fits into the
ImageableArea).