Yeah 100-120 speed would be pretty good for 3 reasons:
1). You can navigate through asteroid fields without using cruise and running into something every 2 seconds.
2). 80 speed is too slow if you cant use thrusters to get places.
3). Fighters have too many advantages against battleships: speed, manuverability, and size. with higher speeds fighters cant jjust fly around a battleship using thrusters while the battleship only does mediocre damage.