I also want to change the default ship form the campaign and training... the (Myrmidon)... I want to change it to another ship.
If I follow what you said... will it also change the default ship?
Assuming you already extracted the ships table from the root.fs2.
The default player ship must be edited in the ship table to change it.
These two lines are near the top of the ships table,
Shown bellow, make your changes in this line from GTF Ulysses to whatever ship you are using.
#Default Player Ship
#Name: GTF Ulysses <-- (change name )
I hope this helps, im not an expert.
