Grow Box for a single plant

Hello everybody, I am a first time grower looking to grow only a single plant or two in a homemade grow box. My idea was to make it out of 3/4" plywood, with the dimensions 3' wide by 3' deep by 6' high. I was going to have holes drilled towards the top on the either side for some cross ventilation. I was going to suspend a 3' long 2-light fluorescent fixture from the top that can be moved up as the plant grows. For the inside I was going to paint it semi-gloss white for reflective purposes and I was going to have the plant in a 5 gallon bucket suspended over a rubber catch basin for drainage and I figured the excess water in the catch basin would create sufficient humidity. I would be kept in a locked garage so it would be fairly safe. Any advice or input from anyone would be greatly appreciated, please lemme know what you think!