Replacing some lights on top of front elevation of really tall building, once in 25 years scaffolding job. At present in MI, but due to roof works this will have to be stripped out. The new lights are going to be 100W LED units. The new roofing structure has ducting approx the size of MT3 built in to it and openings are to be made where the lights have to go. What cable would you use? Note: this is a marine enviroment Note 2: I got to the top of the scaffolding and had to wimp out, much to the amusment of my work mates.