400 watts of heat, expect to use a good vent fan. Also you will need lots of incoming fresh (cool) air. Then your going to need something to kill the great smell of growing pot. Us you hand for the distance to the top of the plants. If you do not you will have a small oven.
Use a attic fan controler to run your vent fan.
Also note the size of plants from grow to bloom, 2x-4x at finish
12 in =36 in plus at finist, bulb clearance , plus bucket. Its going to be real tight, to say the least.