1.The max number of commanders allowed to participate in your rally or reinforcement is 10 (excluding yourself).
2.One commander can have up to one queue of units from another commander in their Command Center.
Super Weapon - Joint Defense:
1.The max number of commanders that can reinforce you in Super Weapon - Joint Defense is also 10.
2.The units in Super Weapon - Joint Defense won't occupy the reinforcement units capacity of the reinforced commander.