I'm not sure how to argue this without it seeming silly or whiny, but.
The Peacemaker is a much bigger spacecraft internally, has 4 cargobays and a full array of internal armaments, and fittings for potentially 19 crew, another 8 fighter pilots, and the fuel for a long-range patrol.
The Lancer is a smaller spaceframe, has 3 smaller, irregularly shaped cargobays, and is just barely big enough to comfortably stand up inside. All the mass the peacemaker uses for it's internal armaments and for keeping an extra 13 people alive, goes into the external hardpoints fitted to the Lancer. It's got a higher carrying capacity because it's using less mass for other stuff. It carries up to 5 human crew, and has no internal weapons.
Even a Blackbird can carry 4 Zigs mounted externally, and has onboard weaponry.
Could handwave it away as the Lancer's continuously variable drive field not being able to accommodate too much external interruptions of the craft's skin. By retracting the wings and using a pair of sensor probes on the nose to continuously monitor the field status, and powerful computers continuously adjusting the sweep angle of the wings to adjust the field geometry as tight as possible to the spaceframe keeping things stable
Oh, and try
Mibbit If that finely crafted link works, it should bring you right in.
EDIT: This is really something that needs BA's input anyway.
Edit the 2nd: Because I've had some time to think, and because using real-life numbers was asking for trouble on my part and I should've known better. 3 Internal bays, 6 external hardpoints. Internal mass 20 tons, external mass 5 tons. Unloaded top speed, .12... loaded top speed, .1.... with external stores, .8. Knightwing's carrying 4 tons in the rear cargobay (Motoroids + equipment). 4 in the center (Hardsuit + life/crew support), and the forward has been modified to extend the crew compartment for an extra 4. (2 beds, a cooking area, and an elegantly compact shower/WC)
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--m(^0^)m-- Wot, no sig?