I have to strongly recommend the Invincible-II forecastle. A significant number of endgame ships will need it. In order to use an Enterprise forecastle and still reach the adult sectors (17+), you'd have to use at best an Enterprise aftcastle, and that's really low retrieval. Bronco and Invincible Forecastles can't reach the endgame sectors at all. An Invincible-II forecastle allows for any aftcastle. When I was trying to design ships for minimal parts overlap so we could make one of each and have that be enough, I kept winding up with having three Invincible-II forecastles between the four ships, with nothing else overlapping.