first off, a 20 watt floro is not nearly enough light unless you had it strapped to the stem. if all you have is the one 20watt and 150 watt i would say put the hps about 8 in. above the plant and the floro on one side of the plant facing the white paint for reflection like you said. water a few times a day. how tall is it by the way? good luck growing. hope this helps.