Thinking about a wider rear tire

[ingobohn_imp]

Not necessarily true. As the CB 1100 has no mandatory tyre brand or name in the registration documents all they (can) control is the tyre dimensions. Will be OK.
The whole thing is a purely German topic by the way - my Dutch colleagues use any tyres that will fit their bikes.
(Still I'd also rather use tyres which have been tested on the bike, and recommended by the manufacturer.)

Well, some say so ... and some not. My father is police man, and he says that for bikes there is a general ("fuzzy") regulation that tires must have an official "permit" (Unbedenklichkeitsbescheinigung) either from the bicycle manufacturer or the tire manufacturer. It is true that the general "tire binding" or even restrictions to a single tire type and model are obsolete. But just having the right dimensions, speed index and load index is not enough ... especially when it comes to an accident and police and insurance need a scapegoat.
And I do not want to try that out...

For example: My old Transalp was shipped with stock tires from Metzeler (Tourance) but nevertheless in a special "U" modification (reinforced). If you use the same tire without U, you drive without technical "OK" form Honda. I called Metzeler in Munich and they confirmed that the "U" model was specifically made for and requested from Honda for the Transalp.