Sir i would like to understand the merits and de-merits of having "offset vertical fin with ventral fin over conventional centralised fin in single main rotor and tail rotor helicopter".......am a student of aero.
If you are referring to a canted tail rotor, then Nick Lappos explains it somewhere deep within the S76 thread, as a means to provide a vertical thrust element to expand the aircrafts longitudinal C&G. Loads of amazing info on this site if you are prepared to dig down and search for it.