[dogscoff]

I can see the "realism" argument that better engines ought to make the ship faster, but on the other hand I can see PvK's point about slowing down expansion by slowing down colony ships. I guess you could make up some technobabble about the colony component beiong too fragile or something, but it doesn't really matter.

Perhaps a compromise would be to research a seperate tech area (further research in colonisation, starliners, ship construction & propulsion?) to get a better, potentially faster colony hull.