Consider the final, 1996 specifications of MD-XX:

http://md-eleven.net/MD11-MD12-undeveloped-models

What are interesting to see here:

The wingspan, 64,8 m or so, fits the 65 m box much like B747-400 and B777-300ER.

The wing reference area is 483 sq m. Considerably bigger than the wing of A340-600 and B777-300ER, but smaller than B747-400.

MTOGW is 365 tons. Compare with 350 tons of B777-300ER, 368 tons of A340-600 and 380 to of A340-600HGW.

The fuselage stretch is less than that of 777. The total lengths are MD-11 61,7 m, MD-XX Stretch 71,2 m, B777-200 63,7 m, B777-300 73,9 m, A340-500 67,9 m, A340-600 75,3 m.

The main gear arrangements are MD-11 4-2-4, B777 6-6 unchanged, MD-XX 6-4-6, A340-600 4-4-4. Thus MD-XX would have as many main wheels as B747.

The engine thrust was only slightly increased compared to MD-11. 62 000 to 65 000 pounds is just 5 % increase, while MTOGW was increased by 28% or so from 285 tons of MD11ER. Then, wing area was increased by over 40 %, so MD-XX would have lower wing loading than MD-11, take off at a slower speed and need less acceleration to reach it at a given runway length.

Was the engine model and manufacturer for MD-XX known?

What was the fan diametre supposed to be?

What was the status and current specifications of A340-600, A340-500, B777-300ER and B777-200LR as of 1996?