Is this a 48" long tank? If so, I've seen a few 48" tanks running (2) 400's without issue
If I were going to try it, then running a case fan along the brace would help the brace cool. Would be a pretty cheap diy & could hook to the same timer as the halides.
Some remove the center brace & replace with 1/4" acrylic. Would allow the light to pass thru & that should mean less heat.