Excellent game, Galciv II is. One thing that bugs me though, is that it seems like the way we have the correlation between speed & hull size right now is a bit unrealistic, i.e. large hulls can fit more engines, and thus go much faster than small hulls. Whereas if we try to recall "real life", big ships lumber by, and small ships zip around...
I think we can change this situation if we have "speed" as the result from interaction between "hull weight" and "engine power". i.e., mod the designs to have hull weight criteria for each hull type, and mod the engines so that they give "engine power" rating instead of "speed". More hull weight would require more engine power to move the ship.
That way, we can have for example small fighters with a warp engine zooming by at 3 parsecs perweek, whereas large dreadnoughts using the same single warp engine can barely cough up 1 parsec, for example. We can of course, install more engines to overcome this.
i've never done any modding, so i dunno how easy/hard to implement this... would be interesting to see though.