@Old Smokey : but at least the portion of the bay where the leg is is presumably covered by a door with the gear up (I've never looked that closely at a B737, but I assume it's the wheel portion of the bay with no door.) That would be the more critical part of the bay to cover, since it's more on the wing, the wheel being in the wing/fuselage fairing.
@IBLB it's not quite so simple; yes, there's no "CD" in the equation, but there are things that can affect the lift on the wing that are secondary effects of the drag, if you assume the power setting is adjusted to account for drag changes. Just as there's nothing directly for pitching moment, but that will impact tail lift and hence overall lift.