I asked earlier about building freighters with faster engines. The general reply was that it only allows the route to start sooner, and once started, the freighters was slow down to a predetermined speed.
However, the question now is: Does any freighters in a route require you to pay for their upkeep?
Being able to start a trade route 5 turns sooner is nice and all, but I don't think it is worth an extra 1 bc per turn after that.
