The Hull B having TR8s while those engines are physically smaller than the Constellation's TR5s would be ridiculous otherwise unless all ships are having their main engines changed to a new size system.
Cloud Imperium
Remember, TR rating indicates thrust and not size! For the entire hull series, especially efficient thrusters are required, as they may be required to push up to 16 times the mass of the ship.
starfarer.space · Q&A: MISC Hull B