The Marine Corps used to use scrim to break up the helmet and during OIF I many Marines used small peices of camo net zip tied on to their helmets to replicate this. It has since "gone out of style". I only did that to my helmet a few times but unless its done carefuly I could see it interfearing with NVG mounts (you would just have to keep it short in the front) and potentaly being a fire or drip hazard (depending on what you used). I think its a great idea depending on what type of operation you are doing. Idealy it would be a quickly detachable system, where you could put it on your helmet in the ambush or defense position and take it off when moving so it wouldn't get caught on things?