Being longer does reduce the need for big stabs, as does putting a bunch of heavy fuel inside--BUT: the stab was reduced TOO much. A BIG reason for making it so small is to reduce drag. It's too small--MD-11's are quite unstable, pitch-wise. ('Tis why every MD-11 crash is on approach) Uses a special computer-controlled longitudinal stability program. And it's ALWAYS on, like a yaw damper. If it fails, you're not totally screwed, but you will have a hell of a time keeping the right attitude. (An F-16 would instantly fall out of the sky if it lost it's FBW controls, the MD-11 will simply become very hard to handle). If it had DC-10 stabs, it'd fly better, but use more gas.
We need more TWA twin-stripes!