Per Welshman's remarks here, stealth and C3 do not mix as a question of game balance. Null-Sig and Void-Sig are both specifically prohibited from even being mounted on the same design and vehicular stealth armor operates under the same rules as standard stealth in that regard. For 'Mech stealth systems, that leaves Chameleon as the odd man out without any notes on it.
Is that deliberate?
Mod Note: answered in the latest errata.
