if those are the 2w bridgelux chinese mars aqua boxes, those are generally best viewed 8-12 above the tank.
5 inches is enough room behind your tank to use some 1/2 conduit to hang from. if it was me i would take a heat gun to the end of the conduit and stick a metal rod in there and bend an elbow over the tank. you could just say screw it and use an elbow premade and hang it from there. (think a large candy cane attached to your stand and arching above the open water.