Bit like going back to the old Battle of the Twins bikes (BOTT) The likes of Geoff Baines on a 900SS powered 851.
Last year I posted a pic of one of the local bikes that was a BOTT race bike at one time, again a 851 chassis with a 900SS engine with a Dual Spark conversion.
Can't see why it can't be done with a 916 Chassis, I should think a little bit of fabrication is required getting the Swingarm mounted and sorting the rear exhaust downpipe are a few things that spring to mind.
I think the swingarm mounting becomes easier if you go with a S2R engine which already uses a single sided arm
Few links to pics of the UltimaDue
http://www.kaemna.de/pic/gebrauchte/ultimadue1.jpg http://www.kaemna.de/pic/gebrauchte/ultimadue2.jpg http://www.kaemna.de/pic/gebrauchte/ultimadue3.jpg http://www.kaemna.de/pic/tuning//ultimadue05.jpg