I've found the Cepheus Deluxe ship design system to be about the best of any version since '77. Here's a quick example of a 100 DT Free Trader
https://www.dropbox.com/scl/fi/co1nnw0ffncqhy7juwor8/100-Ton-Frontier-Trader.ods?rlkey=80n02jbw6heljkhictzm0vr7t&dl=0
The form (design) flows from the econ rules for a frontier area. Freight and lots of Low Passage customers. It will hold 4 PCs in double occupancy. And though only J1 it can J1 + 1 no sweat and even more if freight space can be spared.
I do love me some Cepheus Engine. :D
Can it do larger than Book 2 ships? I hated needing High Guard for that.
As large as you want. It is calculated around a % of hull size for drives and has spinal mounts
"A large starship may carry massive, fixed-mounted,
Main Guns in addition to its turrets and bays. A main
gun displaces 1000 tons and requires ten hardpoints.
There are three types of main guns, Particle Gun,
Meson Gun, and Gravitic Disruptor. Note that the
Meson Cannon and Gravitic Disruptor ignore armor."
Interesting.
Thank you.