[FT] What would you make this cost ?

I'm thinking about a vapour shroud variant to simulate a cloaking device.

The vapour shroud is:

MASS: 5% of ship's MASS Cost: 3xMASS When active, owner cannot fire any
weapons or launch or recover fighters. Attackers treat owning ship as doubly
screened.

The cloaking device might be:

MASS: 5% of ship's MASS Cost: Ship's MASS? When active, owner cannot fire any
weapons or launch or recover fighters, or have other screens active. For
fighters or missiles to attack the owner, they must be within 2 units at the
end of ship movement. For a ship to target the owner, the ship must
successfully scan the ship (roll 5 or 6 on D6 or get 2 "hits" from a 3D6
"attack" on a doubly screened target (close to
equivalent)), then treats the target as singly-screened.