keep it high enough for the pots or hydro setup, plants distance between plant without burning them, distance to grow and space for the light. remember to vent the heat and light sould not be a problem cause it sould be air tight (except for in out take) and light proof you dont want light coming in during the dark period. a 400 or 600 watt system will work well try to get a air cooled hood it will help with heat and safty. good luck keep us posted