Hi,
I don't understand how to determine before hand when 2 class will be compatible, for the same shipyard... I have a weird (serendipitous) case happening to me: I realized that the SY handling my 75.000 tons tugs, made mostly of engines, group jump engine and a tractor beam can also build the 75.000 tons freighter ships, made mostly of cargo holds! Is that not weird? Is the criteria only based on the price of differing items, and as cargo holds are cheap, it makes the ship compatible?