If you could do it again what would you do

[Ruth]

I don't think you are going to get enough coverage with one penant and think you will have dark corners. I am basing this judging by my 6' long tank that I run 3X400W on. I have the 2 end lights run by one double ballast and it is on a separate timer - so I have my middle light come on at 8am and go off at 6pm then my 2 end ones come on at 10am and go off at 8pm. When it is just the 2 end bulbs lite there is a definate shadow in the center. Don't know if this helps and I am definately no expert on lighting - it's just my observation with my own tank.
R