Are the weight of the guns added automatically?
I was thinking about adding a hidden part with mass properties where the guns in the wings are mounted to get better weight distribution. The weight of the AMMO is figured in, but the guns themselves are “absorbed” by whatever body part they’re in. You can always add a phyLBS property and a phyCylInertia to them to be sure. Guns are just like other objects, they need inertia volumes defined to have mass, and therefore weight. See the note about the undocumented ammoBox on the WWW patch forum. This adds weight according to the number of rounds left for the gun.