Each missile bay or tube holds one missile flight. This includes mass of the fighter itself. Hangar bays and troop housing may be designed to be interchangeable in function by multiplying their mass and volume by 1.25. No spacecraft can have more than two stealth levels. Each cubic meter of stealth measures masses 1 ton.
Signature is a function of mass, engine thrust, tech level and stealth features.
The heavier the ship, and the more powerful propulsion system it packs, the greater the chance of it being detected. Same as for Mass, except use Thrust in tons. OM ships subtract .25 from their signature, NM ones subtract .5. Subtract .25 per level of stealth built into the ship. Multiply the result by five.