I'm taking the whole "realistic spaceship" thing in a slightly different direction:
The Corvette is still realistic in that it has no magical shields, no artificial gravity and no faster-than-light anythings, but I've scaled back the size of the the fuel tanks and radiators. The drive-cone(in yellow on the top left) is a borderline-magical drive reaching efficiencies that are likely borderline-impossible. At around 100 feet from nose to tail, this would be the smallest ship that can carry a militarily useful drive and weapon complement. The lower Corvette carries an auxiliary reactor in order to power the railgun in the nose. Both ships mount two (possibly four?) point-defense gauss cannons in the back.