Without wanting to go too much into the details (you know what happens in size discussions here every time....):
Wing Commander and real world sizes don't mix. Almost everything in Wing Commander fails that comparison (person next to ship). For example if you look at WC1, the Raptor should be 36 meters IIRC. That's pretty large. But when you look at the scene during the launch where the player can be seen sitting in the cockpit and you compare that to the blueprints, then you may notice that something is wrong.
The same happens in WC3. IIRC the arrow is too small, and so is the Hellcat. I forgot the others but I'm a bit surprised that you got some satisfying results with the Thunderbolt. The one time I tried to check this I came to some strange results.
On a larger scale it becomes even worse. When you compare capship and fighter sizes in the cutscenes or (even worse) ingame, you get the funniest results. Of course that has reasons, such as ingame engine limitations. There is no real excuse for the cutscenes, though...
That's a problem when you want to do a mod. It happened to Saga and I'm almost sure it happened to Standoff and other mods, too. There are canonical ship sizes that just don't match anything. Not even each other.
So what to do? Some people will hate you for making the ships the size from the manual, because it looks ridiculous. Others will hate you for making them larger or smaller to fit realistic sizes, because "it's not canonical". It's the kind of problem that leads to arguments like "NO WAY the Raptor can be 36 meters long, it wouldn't even fit in the hangar" and "if you compare the size of the doors either the characters are 6 meters tall or there is a wrong size in the manual for the Victory". Then everybody and their mother starts to call each other and their mothers morons, accuse them they would want to piss all over Wing Commander or similar things, and the topic is closed. People get banned and such things.
And I won't even mention a certain ship that spawns this kind of discussion every. single. time...
btw: The same happens with speed. Don't do the math. You will only get a headache.