Yes - you need to create the model, create the gen ship, modify the events to use the new ship as starting one.
Tutorials available here
That thread is way too big to find anything. Are the guides on the wiki (https://tachyongame.miraheze.org/wiki/Guides/Add_new_Ship, https://tachyongame.miraheze.org/wiki/Guides/GenShips) still valid?