Pick up a copy of Helicopter Aerodynamics and More Helicopter Aerodynamics by Ray Prouty. Read up on what affects hover performance.
Areas to look at - extra (same) blade over Dauphin, ideal A of A, L/D ratio etc etc. One way is good for hover (4 blade N3) the other is better for speed (5 blade 155). Download the Tech Data and compare the performance. The dynamics are very similar - Engines, MGB, Fenestron etc.
EC155 Cat A vertical procedure - NONE. Legacy undercarriage and structure.