Come on mate, never put something that can at worst ignite onto flammable material ala, 3 x 2 studding, at least put a ceramic tile under ballast between wood, i always err on side of safety, ya wanna see the amount of rcd's i use, along with contactor relays, and i'm only running a single 315cdm, i had two ballasts burn out internally a few years ago, only due to the my using rcds which had tripped out the electric did i find out, had i not been using them, i'd be brown bread now, i looked and checked everything and all looked good, my last only option was to open up both ballasts, melted everywhere wtf uk420man