I was conflicted by the "cap armor" but I think it just should be "armor" and then the conflict isn't there so much.
Have two versions Just like now and just change the names.
Smaller ships mounting it lose proportionally more of their cargo space which is realistic and the armor is a multiplier and works from what's already there--that's realistic too.
The only real beef I have with the armor is MASS. It should increase the mass--decrease all maneuver and acceleration.