Tiff,
Until 3 weeks ago, I had a 400w MH right over my center brace and it was only 5" away from it. Sure it got hot, but never did any damage. I however recently moved all my lights up to 10" above the water. Not because of the brace though, but rather because I was tired of burning my elbows and arms on them whenever I was working in the tank and also because I am now believeing that most corals don't really need that much light that close..., even those high light loving shallow water types ( and to a lesser degree because I'm starting to get more into the d
eeper water SPS).
A proper type of topoff activation will never stick.