Clone Commander Cody's command card "Bring It Down!" says "when a friendly unit declares an attack against an enemy unit that has an observation token, you may spend the token. If you do, the attack gains suppressive if the enemy is a trooper unit, and impact 1 if the enemy is a vehicle unit.
If the enemy unit has multiple observation tokens can we spend multiple to stack the impact 1 effect? for example, if the unit has 2 observation tokens can both be spent when the attack is declared to gain impact 2?