Here is the rule:

7.34 Torque Box Repair
All cars are allowed to repair or reconstruct the rear lower control arm body attachment points within the following restrictions:
1.The attachment point must remain in the OEM Stock location and maintain the same geometry.
2. All additional reinforcement material or welding of existing material must be within 12” of the centerline of the mounting point hole.
3. None of the additional reinforcement may penetrate the floorpan or enter the interior of the car.
4. None of the additional reinforcement may attach directly to the rollcage or rollcage mounting points
Ford cars are additionally allowed to completely weld the rear upper control arm body attachment points within the following restrictions:
1.The attachment point must remain in the OEM Stock location and maintain the same geometry.
2. All welding of the existing material must be within 10” of the centerline of the mounting point hole.