Looks like 5 might be a hard-coded limit at the moment - I've gone through every file I can find, and not seen anything that looked like it would enable >5 cap ship types... You can have any number less than 5, just not a single one more (:( I think that there's a similar issue with adding extra fighter types - you can create different fighter squad types, which will work, but it seems you can't assign more than two types to one structure/carrier type... I hope this gets looked at in a fu
SimRex
I don't know how the unit cap worked before, when it was based on size of empire, but I'm assuming it was a linear thing - unit cap = planets * num_ships_per_planet. Perhaps, instead of/as well as the research, the number of planets could be taken into account but on a logarithmic scale? ie, for the first few planets, the cap increases rapidly, but gradually the rate of increase in unit cap reduces until capturing a new planet would only allow you an extra heavy cruiser or two, with th