
sgtarbuckle |

The problem with using ship mass/size for skill DCs is that there is no real need to make your ship bigger at higher levels. You would generally have to be of higher level if you want to make your ship bigger, but if you don't want to make your ship bigger, there is no real reason to do so -- especially if all of your skill DCs are getting easier because your ship is staying the same size.
If the ship stat that controls skill DCs is in any way under player control, the players will have a strong incentive to keep that stat as low as possible, whatever it may be.
I really don't see that as a problem. If the players don't want a larger ship I don't think they should be railroaded into having one. And really I doubt any of my players are going to want to go too large anyway with the logistic considerations that come with it. The point of characters progressing is that they get better at doing things. And the heart of the original discussion I believe was why characters are being penalized for making their ship better.