I reviewed the 2 hits Battleship values to 2.5 multiplier factor.
It is an approximation but this is easier to use this value if you need to assess between two naval fleet during a live game with no AACalc allowed.
It is based on the very even (almost 50%-50% survival equilibrium ) combat between 1 Destroyer @2 and 1 Cruiser @3 against 1 Battleship, 2 hits @4.
1 Destroyer @2 and 1 Cruiser @3
5 pips * 2 hits = 10 pips*hits
1 Battleship, 2 hits @4.
4 pips * 1 BB worth 2.5 hits = 10 pips*hits