Well in my opinion the whole purpose of running them vertical is to increase your yield from the base of the plant to the top.. you no longer get just get fat colas .. all the side branching becomes pretty large as well because it receives the same amount of light as the top of the plant. I suppose you could run bare bulbs hanging .. But you would have to make sure the plants or your skin never contacts them.. or your gonna have a scar. WHats the purpose if you dont get the larger yield from running the bulbs from bottom to top? All you doing is allowing more heat into your room that you have to exhaust or cool. IF your purely just trying to get more lumens to the plant.. you can just increase the speed of your fan and drop the air cooled hoods right ontop of them... which negates removing the glass and having to keep them higher up to not burn the plants... The reason most grows have moved to air cooled hoods is because the amount of heat the bulb emits is most efficiently removed in a closed system not allowing it to enter the grow area.
Now if we lived in a mild climate area where keeping the grow room WARM was hard.. then I see no drawback from running uncooled hoods.. but this is socal.. all we fight is heat.. we live in a desert .. so I see no real reason to adding more heat that you have to pay to remove very inefficiently with a portable AC..
Also using CO2 becomes alot harder as well if you cant exhaust the bulb heat independently .....