For the purposes of the Tactical Combat System, Beyond the Horizon's will usually use one of two scales.
Toward the beginning or end of a journey, while starting velocity is still low, use a 100 mile/hex map with 3 minute turns.
This gives a starting velocity of (mps*2), a thrust rating of (G*2), and burn points equal to (current dV*2).
In the middle of a journey, when the ship is going quite fast and maneuvering is limited, use the Basic Combat system.