I'm not seeing if Holomask and Holoprojector can be combined. Meaning, more than one echo as well as masked. I think now it's on or the other. So a Lu Duan can mask as one bike. Going to be easy to spot if it also uses minelayer to place a Deployable Repeater. Luckily it's an optional skill.
Nope, holomask and holoecho can be combined. It's in the holoecho skill description, pg123. So masking as 3 bikes is possible. Kums have ava4 so you can deploy 4 bikes and have the oppo guess what they are exactly.
