you can just hang the bare bulb in there, that is what i was going to do but i know my room and temp that i get upto in summer and winter plus the humidity problems i have at different times of the year. i opted for the cooltube just incase i needed to move heat away at some point.
im new to vertical growing myself, i know that i will achieve a better yield with practice, than i could otherwise with my other methods.
the only reason i went with the cooltube is because of 2 things:
1: i am using a smaller diameter setup so i need to protect my buds from heat.
2: i dont have any ducting connected up to the cool tube as i dont need it right now but when summer gets here again i probably will need to fan the heat away.
when you move air away from your plants you also move the humidity in the air too, i will more than likely have to use a humidity mister to put humidity where i need it at some point in the hot season. possibly even when winter hits its coldest, as the air is dry then.
by the way, 9 oz is nothing to be ashamed of with only 400w bulb. ive hit less with 600w due to poor room conditions when i started out.
i like the idea of vertical growing as you can at least triple your ft or meter square, it is just a matter of time before i dial it in and get what i want.