Graviman,
A negative longitudinal cyclic trim example would be hard to come by as certification requirements tend to lead designers to eliminate that feature. Under certain flight conditions, most helicopters could demonstrate this. I've seen neutral in a few.
Manoeuvre stability took a bit for me to get my head around until one quick flight. An increase in rotor thrust will normally create a pitch up moment. To eliminate this you need forward cyclic. If you manoeuvre aggressively, you may increase power and pull aft cyclic to generate a pitch rate, the higher the pitch rate, the more aft cyclic. However, once the pitch moment from the rotor dominates, you'll find that your cyclic will have to be forward to maintain a higher pitch rate. When that happens, you have negative manoeuvre stability. It makes it difficult to fly the helicopter with any precision, and could cause the helicopter to "dig in" and suddenly create more pitch rate than you wanted.
As far as the inherent tilt to the rotors of a tandem, I could only guess.
Matthew.