So I'm designing some fully armed and operational stock ships for an upcoming campaign, and omg there are a lot of potential for mods on engines, hulls, hyperdrives, etc. What would be a good default assumption regarding how many and what kinds of mods were installed? Zero seems unsatisfactory and un-competitive with stats for existing craft, and All seems absurd. Thanks.

ETA: My purpose is to, rather than re-skin existing ones, hand craft the starships for an OR game. The FO method results in hardier ships with more HP, thereby fixing a chief problem with starship combat, but without mods, they seriously underperform compared to the standards.

I would probably put 25/35% of mods for a stock ship, 50% for a commercial product and anywhere between 70/100% for fully stocked vessel of war/something that has been lived in a good while. Really depends on what the ship is and what it's role is.

For example, most Starfighters in this system have very few hardpoints available unless they have been designed to be barebones and modified by the employer. Freighters generally have 4 hard points available, with only the super customisable ships (the YT series) getting more slots.

Technically, a stock ship should not have any mods. That is what stock means

This somewhat depends on the players too. If you have a player who wants his character to tinker with the ship, dont fill all the slots. If you have a group where they dont have any skill in modding then go to town.