Remove lower growth??

My room is 6.5 x 6.5 x 7 with a 600w HPS on one side and a 1000w HPS on the other side. There is enough room to pack 40-42 3gal. pots tightly. I was starting them on 12/12 early to keep them smaller and this was working ok, they would end up being done before they shaded each other out. Today Im alot better at this and I am letting them grow out more before the switch which is helping the overall yeild. My first question is should I be removing thr lower growth in the first week or two after the switch to provent shading and devert the energy to the tops Next question is do I have enough light to go bigger
6.5 W x ?? L x 7 H I can really only go one way.

I know alot of people remove the lower branches for cloning. I've also heard it can increase yield on the top cola. Try it out! Only way to find out!

trimming lower leaves will allow the energy of the grow to hit the higher branches and produce bigger buds. Your yield is not bigger but your buds will be. The pro's use what is called "lolly pop" and take out all the lower branches off to produce massive tops. You can begin this as early as the first week of flower. I would test this out and only trim a few of the lower ones until you see what happens and keep working more and more each grow.
As far as your more plants under the same light goes, You will get less weed per plant and really not gain anything. Your better off with less plants and bigger yields per plant and bigger buds. This chart may help in coverage.

Removing lower branches in a crowded room also increases air flow under the canopy. Increased airflow = more healthy happy plants