If I could have gotten anywhere near 50 mpg with my Termis and open airbox, I would still own that S4RS. Even Imperial gallons.
Not saying I don't believe you, but I have never seen anyone approach that number with any Ducati. My air-cooled bikes, ridden moderately, might on occasion get 45 mpg.
My current 1200 Multi can, when ridden very gently, do 40 mpg...on the freeway. Made it 200 miles exactly twice...sweating bullets each time.
Commuting, with light throttle, is more like 34-36. Again, Termi kit. And that reflects pretty much exactly what I read on every Ducati forum I am a member of (four at last count).