I love the model, it looks both strong and elegant.
Smaller size would seem to translate into greater acceleration / maneuverability do to reduced mass, but also reduced secondary weapons capacity because of little storage space. I would recommend this fighter being more of a heavy defense fighter with lots of primary gun ports and decent maneuverability but few warheads. Slower acceleration and speed once armor is added, but sporting new maneuvering thrusters and avionics innovations resulting in a somewhat slow but very maneuverable fighter.
It also looks like it is could of come from the same development team who designed the Caliburn, so saying it was designed around the generator that the Caliburn was meant to have and that it powers the array of gun ports on the Excalibur would make for some good background info in the tech-room.
So to balance this fighter,
better speed with weaker armor, or slower but with dense armor
stronger shields with less energy for primary weapons
weaker shields but possessing an impressive primary weapons array with lots of weapon energy that could be dumped into shields when you get yourself into trouble
This is my idea with the Excalibur could become but what I really want to say is not to make this fighter too vanilla, it needs to have some trait that sets it apart from all the other fighters, that something that makes you fall in love a that fighter and prefer it over all the others, that defining characteristic that suits your particular style. Why do I feel like I'm writing for a car commercial