i havent read any of the posts in here but i used a 400wtt in a box set up 4x2x5 and it worked well. that cool tube will help mucho. U may expeirence high temps but i dont think they should get too high, just make sure u have proper venting and a high cfm fan. if your balast is safe u have nothing to worry about, your light will not cuase a fire unless u have it directly touching the wood. which to any one would seem stupid. just give space where it is needed.