There is a school of thought that says that hard back protectors have caused needless neck injuries due to not being tied down enough, moving up in an accident an compacting with the base of the skull.
However I say one fitted into a Ducati jacket would be very comfortable, - and you need to be comfortable on a bike. I did have one of those very large, cover all of your back Knox ones, and was so damn restricted I swear it was dangerous wearing it. I sold it and got a more minimal cLOVER jobs.

Few of the racers, Troy and Edwards that I know of wear chest protectors also.

Hipshaker.
I have a spare Dainese back protector which is the same as in your post. It was out of some old leathers that got trashed after a spill. I cannot recomend them enough. My new leathers came with the same protector with them so if you want my spare just u2u me with your address and i will send it down.

hipshaker
I have a brand new full length Dainese back protector ( never worn ) that came with my Dainese leathers I bought at Ducati factory in April this year going cheap if your interested.