Denier,
I think a large engine is needed because of the ship size. Igiss is suggesting that normal speed for battleships (all capital ships) might be increased, that sounds OK. Maybe increase cruise speed as well for cap ships then and thruster speed for light fighters? It would only be a small change, most other ships would travel at "normal" speeds.
Role-played characters:
daedalus - Liberty Navy
bandersnatch - Ruthless criminal possessed by a (huge) alien
Shredder - Small-time Kusari pirate, looking to join the Blood Dragons
"Bounty Hunters. We don't need that scum." - Admiral Piett