These are official rules for The Dark Valley:
Add to 3.1 In General:
"In the Campaign Game (only ) the Oil hex W1642 (Nagykanizsa) is treated as a Victory Hex for all purposes starting on Turn 41 (January 1945) only. Before then it has no effect. See also 7.9."
Add to 7.9 Axis Withdrawals:
"Turn ? Withdraw 1 one Air Unit and its Base if the Soviets control all Oil hexes on the map, including hex W1642 (Nagykanizsa). This removal is permanent, even if an oil hex is recaptured by the Axis." [Note: This compensates somewhat for giving the Axis an additional VP in 45.]
17.3.1 Page 7 at end of paragraph beginning “In all cases stacking limits must be observed." Add: “ No more than 24 units (excluding Stavka and/or Zhukov) may set up within range of the Soviet Fortified marker west of the red Fall Blau start line, and these may include no more than one Guard, two Guard Tank, and nine Infantry armies.” [This is roughly the historical limit, and will prevent the Soviets making Kursk attack-proof, but it will still be a very long shot for
the Axis provided the Soviets have kept a Stavka Reserve.]